Northern LineThe Northern Line begins alongside the Northeastern Line up until Ban Phachi Junction. Here, it splits from the Northeastern Line and proceeds through Lopburi, Nakhon Sawan, Phichit, Phitsanulok, Denchai junction, Lampang, Lamphun, before finally reaching Chiang Mai 751 kilometers away from Bangkok. There is also a branch off the mainline from Ban Dara junction to Sawankhalok in Sukhothai Province.
 Northeastern LineThe Northeastern Line begins on the same route as the Northern Line, splitting at Ban Phachi Junction towards Nakhon Ratchasima. Then at Thanon Chira Junction, the line splits with one route passing Khon Kaen and Udon Thani before terminating at Nong Khai 624 kilometers from Bangkok. The other route passes through Buriram, Surin, Si Sa Ket to reach Ubon Ratchathani, 575 kilometers from Bangkok.
There is also another branch route originating from Kaeng Khoi Junction in Saraburi Province passing through Lamnarai in Lopburi Province, Chaturat in Chaiyaphum Province, before joining the mainline heading towards Nong Khai at Bua Yai Junction in Nakhon Ratchasima Province.
 Southern LineThe Southern Line begins in Bangkok and heads west towards Nakhon Pathom before splitting into 3 different routes. One route heads west towards Kanchanaburi Province (km 210) while another heads north towards Suphan Buri (km 157). The Southern Line itself continues southbound through Ratchaburi, Phetchaburi, Hua Hin, Prachuap Khiri Khan Province, Chumphon, to Surat Thani 678 kilometers away. From Surat Thani, there is a westerly branch towards Khiri Ratnikhom while the main line continues south to Thung Song Junction in Nakhon Si Thammarat Province where another branch reaches Kantang in Trang Province. The main line from Nakhon Sri Thammarat continues through Phatthalung before reaching Hatyai Junction in Songkhla Province. From here, the line branches to connect with the Malaysian railway at Padang Besar and Sungai Golok passing through Yala Province in the process.
 Eastern LineThe Eastern Line begins at Bangkok before heading through Chacheongsao, Prachinburi to terminate at Aranyaprathet station in Sa Kaew Province 255 kilometers later. There is an unused rail link to Cambodia from Aranyaprathet. A branch line also connects Khlong 19 to the Northeastern Line at Kaeng Khoi Junction. At Chacheongsao station, there is another branch to Sattahip from which there is also another branch to Sriracha Junction 139 kilometers from Bangkok. From Sriracha Junction, there is yet another branch towards Laem Chabang deep sea port and Mapthaphut.
 Other linesThe Maeklong Railway is a line operated by the State Railway of Thailand. It is independent of the national rail network and is split into two sections. The line begins at Wong Wien Yai in Bangkok before terminating at Mahachai where a ferry is used by passengers to cross the Tha Chin river. The line starts again across the river towards Mae Klong.
 Rail transport in BangkokIn the late 1800s and early 1900s, King Rama V eagerly built a tram network for Bangkok by employing foreign engineers and technicians, especially Danish engineers. In fact, Bangkok had electric trams before Copenhagen. However, due to a lack of interest and maintenance the tram network was completely scrapped in 1968.
Bangkok's first modern mass transit system, the BTS Skytrain, was opened on 5 December 1999. It consists of 23 stations and 2 lines with a combined route length of 23 kilometers and are run by 35 3-car EMU trains built by Siemens. The railway uses third rail at 750 V DC and unlike the mainline railway, is standard gauge. On 3 July 2004, the Bangkok Metro, a 21 kilometer 18 station underground mass transit rail line was opened and is serviced by 19 3 car trains very similar to the Skytrain. In 2007 a record number of passengers per day on the Skytrain increased to nearly 400,000 while the number of passengers for the Metro increased with 190,000 people per day.
 OperatorsAll intercity rail transportation is managed by the State Railway of Thailand, a government agency responsible for rail infrastructure investment as well as freight and passenger services.
In Bangkok, the Skytrain is operated by Bangkok Mass Transit System Public Company Limited (BTSC) under a concession granted by the Bangkok Metropolitan Administration (BMA) but the investment for the structure and system were fully supported by BTSC. The underground system is operated by Bangkok Metro Company Limited (BMCL), while whole project investments were shared by Mass Rapid Transit Authorities (MRTA) and BMCL, which all civil structures was provided by government sector and the system was provided by private sector (BMCL). The deal of contract between BMCL and MRTA are under the concession agreement for 25 years operation.
 FutureThe Suvarnabhumi Airport Link is a high speed train route currently being constructed by the State Railway of Thailand linking Suvarnabhumi Airport and Phaya Thai BTS Station as well as Makkasan station, which is also set to serve as the City Air Terminal. It is expected to be operational by August 2010.
Mass transit routes in Bangkok is also set to be expanded. Excluding the already under construction extensions to the Skytrain, the Bangkok Metropolitan Government is planning a northern as well as western expansion of the Skytrain. The Central Government, through the State Railway of Thailand and Mass Rapid Transit Authority of Thailand are also planning to build several new metro routes, three of which will begin construction by year end.
The Thai Government also has double tracking projects including a double tracking project currently in the works between Laem Chabang deep sea port and the Lad Krabang ICD. Also, in line with the Government's policy of reducing overall logistics costs in Thailand, there are plans to completely double track all the main lines in the country as well as upgrade track quality. The Government is also mulling a restructuring of the State Railway of Thailand and granting operating concessions to private freight operators. An international rail link is also being constructed towards Vientiane in Laos via Nong Khai and the Thai-Lao Friendship Bridge.
There is also a plan to construct new railway routes to Chiang Rai in the North via Denchai Junction, to Phuket via Surat Thani, and to connect the Mae Klong railway to the main lines.
In October 2010, the Thai parliament approved initial proposals for a high speed rail network to be built with Chinese industrial partners; 5 lines capable of 250 km/h would radiate from Bangkok.