The land border is based on the 1909 treaty between Thailand, then known as Siam, and the British which started to exert its influence over the northern Malay states of Kedah, Kelantan, Perlis and Terengganu in the early 20th century. The four states had earlier been under Siamese control. Four Malaysian states abut the border. They are (from west to east) Perlis, Kedah, Perak and Kelantan. The four Thai provinces which abut the border are (again from west to east) are Satun, Songkhla, Yala and Narathiwat.
Malaysia and Thailand have a territorial sea and continental shelf boundary agreements for the Straits of Malacca which was signed in 1979 and 1971 respectively. The 1979 agreement also included Indonesia as a signatory as it also determined the common continental shelf border tripoint for the three countries. The 1979 agreement also established the territorial sea boundary in the Gulf of Thailand while a separate memorandum of understanding signed in 1979 established a short continental shelf boundary in the area. The boundary beyond that agreed is subject to dispute because of overlapping claims over the seabed. The overlapping claims led to the establishment of a joint development area in 1990 where both countries agreed to share mineral resources in a 7,250 square km wedge-shaped area.
 Land borderPerlis River estuary as defined in the schedule of the Anglo-Siamese Treaty of 1909 where the western most land boundary terminus was to be at "the most seaward point of the northern bank of the estuary of the Perlis River".
The treaty then states that the border moves northward from this point to the Sayun Range, an extension of the Si Thammarat Mountains of Thailand, for about 15 miles (24km) before heading eastward along the watershed of Thailand's Lam Yai River and Malaysia's Perlis River towards the ridge of the Kedah-Singgora mountains where it moves soutwards along the ridgeline till it reaches the watershed for the Perak and Pattani Rivers.
The border then moves eastward across the northern part of Peninsula Malaysia's Main Range (Malay: Banjaran Titiwangsa) along the watershed of Malaysia's Perak River and Pergau River (in Kelantan) and Thailand's Pattani and Sai Buri Rivers until it reaches Bukit Jeli. An 8 km stretch of the border around Bukit Jeli is being disputed by both countries (see below).
From Bukit Jeli, the boundary follows the Golok River until the river mouth at Kuala Tabar, a distance of 95 km. The border follows the deepest part or thalweg of the river.
 Maritime borderMalaysia and Thailand share maritime borders in two segments - in the Straits of Malacca and in the Gulf of Thailand/South China Sea.
 Straits of MalaccaAt the western terminus of the land boundary, the 1909 Anglo-Siamese treaty determines the start of the maritime boundary as:
- With regard to the islands close to the west coast, those lying to the north of the parallel of latitude where the most seaward point of the north bank of the estuary of the Perlis River (the western terminus of the Malaysia-Thailand land boundary) touches the sea shall remain to Siam, and those lying to the south of the parallel shall become British."
- The island known as Pule Langkawi, together with all the islets south of the mid-channel between Terutau and Langkawi, and all the islands south of Langkawi shall become British. Terutau and the islets to the north of mid-channel shall remain to Siam.
|Point||Latitude (N)||Longtitude (E)||Remarks|
|Territorial sea border end and turning points|
|1||6° 28'.5||99° 39'.2|
|2||6° 30'.2||99° 33'.4|
|3||6° 28'.9||99° 30'.7|
|4||6° 18'.4||99° 27'.5|
|Indonesia-Malaysia-Thailand common point|
|CP||5° 57'.0||98° 1'.5||The border is a straight line connecting the common point with Point 1 below|
|Outer limit border turning point coordinates|
|1||6° 18'.0||99° 6'.7||The border connects to the common point above via a straight line|
|2||6° 16'.3||99° 19'.3|
|3||6° 18'.4||99° 27'.5||This point is the same as Point 4 of the territorial sea border|
 Gulf of Thailand/South China SeaAgreements
The 1909 Anglo-Siamese Treaty states that the maritime boundary between the two countries as follows:
- "All islands adjacent to the eastern States of Kelantan and Tringganu, south of the parallel of latitude drawn from the point where the Sungei Golok reaches the coast at a place called Kuala Tabar, shall be transferred to Great Britain, and all islands to the north of that parallel shall remain to Siam."
The boundary beyond the northern end-point is subject to dispute (see Disputes section below). However, both countries have come to an agreement to put aside the border dispute and allow for the joint exploitation of natural resources of the disputed area. The two countries signed a Memorandum of Understanding for the Establishment of a Joint Authority for the Exploitation of the Resources of the Sea-Bed in a Defined Area of the Continental Shelf of the Two Countries in the Gulf of Thailand on 21 February 1979, followed by an Agreement on the Constitution and Other Matters Relating to the Establishment of the Malaysia-Thailand Joint Authority on 30 May 1990 establishing a joint development area (JDA). Both agreements do not settle disputed maritime border and sovereignty issue of the disputed area and the countries continue staking their overlapping continental shelf claims.
Malaysia's 1979 map and Thailand's EEZ proclamation
In December 1979 just after the two countries signed the MOU on the joint development area, Malaysia published a map showing its territorial sea and continental shelf and continued to assert its sovereignty over the entire joint development area. Malaysia's continental shelf boundary on the map corresponds with the western and northern limit of the joint development area.
On 16 February 1988, Thailand issued a Royal Proclamation to establish its exclusive economic zone boundary with Malaysia, establishing the limits of its claims in the disputed area. The boundary follows the eastern boundary of the Joint Devevelopment Area.
A small triangle in the northern portion of the joint development area is also subjected to an overlapping claim by Vietnam. In 1999, Malaysia, Thailand and Vietnam agreed to apply the joint development principles for this area. See section below.
|Point||Latitude (N)||Longtitude (E)||Remarks|
|Territorial sea border end and turning points|
|1||6° 14'.5||102° 5'.6|
|2||6° 27'.5||102° 10'.0|
|Continental shelf border end and turning points|
|1||6° 27'.5||102° 10'.0||Same point as northern terminus of the territorial sea border, also Point 47 on Malaysia's 1979 continental shelf claim map|
|2||6° 27'.8||102° 9'.6||Same as Point 46 on Malaysia's 1979 continental shelf claim map|
|3||6° 50'.0||102° 21'.2||Same as Point 45 on Malaysia's 1979 continental shelf claim map|
|Continental shelf border end and turning points claimed by Malaysia|
|45||06° 50'.0||102° 21'.2||Same point as the northern terminus of the agreed continental shelf border; also Point A of Joint Development Area.|
|44||07° 10'.25||102° 29'.0||Same as Point B of Joint Development Area|
|43||07° 49'.0||103° 02'.5||Same as Point C of Joint Development Area|
|Exclusive economic zone border end and turning points claimed by Thailand|
|1||6° 14'.5||102° 5'.6||Southern terminus of territorial sea boundary|
|2||6° 27'.5||102° 10'.0||Northern terminus of territorial sea boundary and southern terminus of agreed continental shelf border; same as Point 47 on Malaysia's 1979 map|
|3||6° 27'.8||102° 9'.6||Same as Point 46 on Malaysia's 1979 map|
|4||06° 50'.0||102° 21'.2||Northern terminus of the agreed continental shelf border; same as Point 45 on Malaysia's 1979 map; also Point A of Joint Development Area.|
|5||06° 53'.0||102° 34'.0||Same as Point G of Joint Development Area|
|6||07° 03'.0||103° 06'.0||Same as Point F of Joint Development Area|
|7||07°20'.0||103° 39'.0||Same as Point E of Joint Development Area|
|8||07° 22'.0||103° 42'.5||Same as Point D of Joint Development Area, located on Malaysia's continental shelf border between Point 43 and Point 42 on 1979 map|
 HistoryThe border between Thailand or Siam and the sultanates of the Malay Peninsular (Peninsula Malaysia today) has varied throughout history according to the influence the kingdom over the sultanates. The southern part of Siam has always been populated by Malays and traditional Malay sultanates of Kedah (of which Perlis was part), Kelantan, Pattani (which consist of the areas of Singgora, Yala, Ligor and Setul) and Terengganu came under Siamese suzerainty in the 19th century. The Malay states to immediately to the south, namely Perak and Pahang were independent sultanates until the British started asserting influence over them in the late 1800s. The frontier between the states were largely vague and not well defined.
In 1785, the British obtained the island of Penang from the Sultan of Kedah. The channel between the island and the mainland of Peninsula Malaysia became the border between British territory and Kedah, and therefore Siamese, territory.
On 6 May 1869, Great Britain and Siam signed an agreement known as the Bangkok Treaty of 1869 where Siam ceded a piece of territory on the mainland opposite Penang to Great Britain. The territory became known as Province Wellesley (known as Seberang Perai today). The treaty also defined the border between British and Siamese territory and this border remains the boundary line between Penang and Kedah today, although both are now constituent states of Malaysia.
On 9 July 1909, Great Britain and Siam signed another agreement in Bangkok. Known as the Anglo-Siamese Treaty of 1909, the agreement ceded the states of Kedah, Kelantan and Terengganu to Great Britain while Pattani remained in Siamese hands. The treaty, in one of its four annexes, defined the border between British and Siamese territories. This border ultimately became today's border between Malaysia and Thailand.
Thailand regained control of the Kedah, Kelantan and Terengganu during World War II when the Japanese handed them over to the kingdom, thus moving the Malay States-Siamese border southwards again. However, the states were returned to the British at the end of the war.
 DisputesThere are two stretches of the Malaysia-Thailand border which is subject to dispute. The first involves the land border in the Bukit Jeli (Jeli Hill) at the headwaters of thye Golok River and the second involves the continental shelf boundary in the Gulf of Thailand. Both disputes have not resulted in any aggression between the two countries.
 Bukit JeliThe alignment of an 8.5 km stretch of the land border in the area known as Bukit Jeli (Jeli Hill) near the headwaters of the Golok River is currently being disputed by both countries. The resulting disputed territory has an area of 42 hectares. Negotiations to resolve the dispute through the joint subcommittee on cooperation along the border is on-going. The dispute arose in the 1990s when demarcation work for the land border almost reached completion. Malaysia's former Foreign Minister Syed Hamid Albar was quoted as saying that the failure was because of the inability to reach a consensus over a formula to solve the dispute. He said problems arose because the geographical features as described in border protocol of the 1909 Anglo-Siamese Treaty had changed.
 Gulf of ThailandThe dispute over the continental shelf boundary between Malaysia and Thailand arises from the different baselines for Thailand which the two countries adopt in calculating the equidistant line for boundary. Thailand's proclaimed baseline runs from the terminus at Kuala Tabar (the eastern terminus of the Malaysia-Thailand land border as defined by the 1909 Anglo-Siamese Treaty) northwards to Ko Losin islet and then northwestwards to Ko Kra. Malaysia however does not regard Ko Losin as valid baseline point and calculates the equidistant line on a baseline running along the shore.
While both countries have agreed on 24 October 1979 on their maritime boundary for this area running 29 nautical miles (54 km) out to sea, the boundary beyond the northeastern terminus of the territorial sea is subject to dispute. Malaysia's continental shelf boundary extends from the terminus at coordinate 07° 49' N, 103° 02' 30" E which corresponds to Point 43 in a 1979 map published by Malaysia denoting its territorial sea and continental shelf. Thailand claims its continental shelf boundary extends from the terminus to coordinate 07° 22'.0 N, 103° 42' 30" E. A small slice of the disputed area is also subjected to a claim by Vietnam.
As a temporary solution to the dispute, Malaysia and Thailand on 21 February 1979 signed a memorandum of understanding to create a 7,250 km square joint development area encompassing the entire disputed area. This was later followed by an agreement on 30 May 1990. The agreement allows for joint exploitation and benefit of natural resources in the joint development area. In 1999, Malaysia, Thailand and Vietnam reached an agreement based on the principal of joint development for the area where the three countries have overlapping claims. All the agreements specifically state that they do not compromise each country's sovereignty claim over the disputed area.  See section below for more on the joint development area.
 Joint development areaThe Malaysia-Thailand Joint Development Area is a 7,250 km square area in the Gulf of Thailand which was created as an interim measure to deal with the overlapping claims of the continental shelf between the two countries. The formula allows for both countries to share the non-living natural resources from the area on a 50:50 basis. It however does not extinguish the sovereignty claims by both countries over the area.
|Point||Latitude (N)||Longtitude (E)||Remarks|
|Joint Development Area boundary turning points|
|A||6° 50'.0||102° 21'.2||Northern terminus of agreed continental shelf border; Point 45 on Malaysia's 1979 map; Point 4 of Thailand's EEZ border|
|B||7° 10'.25||102° 29'.0||Same as Point 44 on Malaysia's 1979 map|
|C||7° 49'.0||103° 02'.5||Same as Point 43 on Malaysia's 1979 map; Point C (eastern terminus) of the agreed Thailand-Vietnam continental shelf boundary.|
|D||7° 22'.0||103° 42'.5||Same as Point 8 of Thailand's EEZ border; located on Malaysia's continental shelf boundary between Point 43 and Point 42 in the 1979 map.|
|E||7° 20'.0||103° 39'.0||Same as Point 7 of Thailand's EEZ border|
|F||7° 03'.0||103° 39'.0||Same as Point 6 of Thailand's EEZ border|
|G||6° 53'.0||102° 34'.0||Same as Point 5 of Thailand's EEZ border|
|Coordinates of area within the joint development area claimed by Malaysia, Thailand and Vietnam|
|1||7° 48'.0||103° 02'.5||Same as Point C of the Malaysia-Thailand JDA boundary; Point 43 on Malaysia's 1979 map; and Point C (eastern terminus) of the agreed Thailand-Vietnam continental shelf boundary.|
|2||7° 22'.0||103° 42'.5||Same as Point D of the Malaysia-Thailand JDA|
|3||7° 20'.0||103° 39'.0||Same as Point E of the Malaysia-Thailand JDA; same as Point B of the Malaysia-Vietnam joint development defined area boundary.|
|4||7° 18'.31||103° 35'.71||Located along the south-eastern border of the Malaysia-Thailand JDA between Point E and Point F; same as Point C of the Malaysia-Vietnam joint development defined area boundary. The boundary then continues back to Point 1.|
See the Malaysia-Thailand joint development area page for more details.
 BarrierIn the 1970s, both Malaysia and Thailand constructed walls along their common border, mostly in Perlis/Satun and Perlis/Songkhla as well as Kedah/Songkhla portions of the border to curb smuggling. The walls were of concrete, steel and topped barbed wire as well as iron fencing at other stretches. As both countries constructed their own walls a little into their own territory, a strip of "no-man's-land" about 10m wide was created and this strip of land became a convenient refuge for smugglers (not all smuggling was deterred by the wall) and drug runners.
In 2001, the two countries agreed to construct just one wall along the border which would be located just inside Thai territory. The new border wall is 2.5m high and made up of a concrete lower half and steel fencing on the upper half. At the base, barbed wire runs along the length of the wall.
While the stated reason for the construction of the wall has been to curb smuggling and encroachment, security reasons - earlier in the 1970s and 1980s resulting from Malaysian communist groups and groups involved in the South Thailand insurgency in the late 1990s and early 2000s - have also been a major push for the barrier to be constructed.
 Border crossings
 Road crossings
- Wang Kelian/perlis - Wang Prachan/satun
- Padang Besar/perlis - Padang Besar (Songkhla)
- Bukit Kayu Hitam/kedah - ban danok/Sadao/songkhla
- Pengkalan Hulu/perak (previously known as Keroh) - Betong/yala
- Bukit Bunga/jeli/kelantan - Ban Buketa/weng/narathiwat
- Rantau Panjang/kelantan - Sungai Golok/narathiwat
- Durian Burung/from kuala nerang + alor setar/kedah - Ban Prakob/na thawi/songkhla
 Railway crossingsThere are two rail crossings along the Malaysian-Thai border.
- Padang Besar-Padang Besar (Songkhla): Both the Malaysian and Thai towns where the crossing is located are known by the same name. This crossing connects to Malaysia's West Coast trunk line and Thailand's main southern line to Bangkok via Hat Yai. Both Malaysian and Thai customs, immigration and quarantine formalities are conducted at Malaysia's Padang Besar railway station.
- Rantau Panjang-Sungai Golok: On the Malaysian side, this bridge crossing is on a branch line which is connected to Malaysia's East Coast line. In Thailand, the crossing is connected to the Sungai Golok branch line which links up with the main southern line at Hat Yai.