By the 11th-12th centuries, Mon Influenced over central Thailand. Khmer cultural influence was brought in the form of language, art and religion. The "Sanskrit" language was entered in Mon-Thai vocabulary during the Khmer or Lopburi Period. The influence of this period has affected many provinces in the north-east such as Kanchanaburi and Lopburi. The Architecture in "Angkor" was also constructed according to the Khmers style. The Khmer built stone temples in the northeast, some of which have been restored to their former glory, those at Phimai and Phanom Rung and further cultures are stone sculptures and stone Buddha images. Politically, however, the Khmer cultural dominance did not control the whole area but power through vassals and governors.
After the death of King Tilokoraj, the kingdom suffered from internal conflicts. Lan Na weakened because of wars with Sukhothai's successors.
The Thai kings of Ayutthaya became powerful in the 14th and 15th centuries, taking over U-Thong, Lopburi, and Ayutthaya. Ayutthaya's first king, Ramathibodi I, was both a warrior and a lawmaker. Some old laws codified in 1805 by the first Bangkok king date from this much earlier reign. King Ramathibodi I and his immediate successors expanded Ayutthaya's territory, especially northward towards Sukhothai and eastward towards the Khmer capital of Angkor. By the 15th century, Ayutthaya had established a firm hegemony over most of the northern and central Thai states, though attempts to conquer Lanna failed. Ayutthaya also captured Angkor on at least one occasion but was unable to hold on to it for long. The Ayutthaya kingdom thus changed, during the 15th century, from being a small state primus inter pares among similar states in central Thailand into an increasingly centralized kingdom wielding tight control over a core area of territory, as well as having looser authority over a string of tributary states.
King U-Thong and his immediate successors expanded Ayutthaya's territory, especially northward towards Sukhothai and eastward towards the Khmer capital of Angkor. The greater size of Ayutthaya's territory, as compared with that of Sukhothai, meant that the method of government could not remain the same as during the days of King Ramkhamhaeng. The paternalistic and benevolent Buddhist kingship of Sukhothai would not have worked in Ayutthaya. The king of the latter therefore created a complex administrative system allied to a hierarchical social system. This administ rative system dating from the reign of King Trailok, or Borommatrailokanat(1448-1488), was to evolve into the modern Thai bureaucracy. The Ayutthaya bureaucracy contained a hierarchy of ranked and titled officials, all of whom had varying amounts of "honor marks" (sakdina). Thai society during the Ayutthaya period also became strictly hierarchical. There were, roughly, three classes of people, with the king at the very apex of the structure. At the bottom of the social scale, and the most numerous, were the commoners (freemen or phrai) and the slaves. Above the commoners were the officials or "nobles" (khunnang), while at the top of the scale were the princes (chao). The one classless sector of Thai society was the Buddhist monkhood, or sangha, into which all classes of Thai men could be ordained. The monkhood was the institution which could weld together all the different social classes, the Buddhist monasteries being the center of all Thai communities both urban and a gricultural.
The Ayutthaya kings were not only Buddhist kings who ruled according to the dhamma (dharma), but they were also devaraja, god-kings whose sacred power was associated with the Hindu, gods Indra and Vishnu. To many Western observers, the kings of Ayutthaya were treated as if they were gods. The French Abbe de Choisy, who came to Ayutthaya in 1685, wrote that, "the king has absolute power. He is truly the god of the Siamese: no-one dares to utter his name." Another 17th century writer, the Dutchman Van Vliet, remarked that the king of Siam was "honoured and worshipped by his subjects more than a god.
The Ayutthaya period was early Thai history's great era of international trade. Ayutthaya's role as a port made it one of Southeast Asia's richest emporia. The port of Ayutthaya was an entrepot, an international market place where goods from the Far East could be bought or bartered in exchange for merchandise from the Malay/Indonesian Archipelago, India, or Persia, not to mention local wares or produce from Ayutthaya's vast hinterland. The trading world of the Indian Ocean was accessible to Ayutthaya through its possession, for much of its 417-year history, of the seaport of Mergui on the Bay of Bengal. This port in Tenasserim province was linked to the capital by a wild but ancient and frequently used overland trade route.
Throughout its long history, Ayutthaya had a thriving commerce in "forest produce", principally sapanwood (a wood which produces reddish dye), eaglewood (an aromatic wood), benzoin (a type of incense), gumlac (used as wax), and deerhides (much in d emand in Japan). Elephant teeth and rhinoceros horns were also highly valued exports, but the former was a strict royal monopoly and the latter relatively rare, especially compared with deerhides. Ayutthaya also sold provisions such as rice and dried fish to other Southeast Asian states. The range of minerals found in the kingdom was limit ed, but tin from Phuket ("Junkceylon") and Nakhon Si Thammarat ("Ligor") was much sought after by both Asian and European traders.
The Chinese, with their large and versatile junks, were the traders who had the most regular and sustained contact with Ayutthaya. The Ayutthaya kings, in order to conduct a steady and profitable trade with Ming and Manchu China, from the 14th to t he 18th centuries, entered willingly into a tributary relationship with the Chinese emperors. The Thais recognized Chinese suzerainty and China's preeminent position in Asia in return for Chinese political sanction and, even more desirable, Chinese luxury goods. Muslim merchants came from India and further West to sell their highly-prized clothes both to Thais and to other foreign traders. So dominant were Chinese and Muslim merchants in Ayutthaya that an old Thai law dating back to the 15th century divides the Thai king's foreign trade department into two: a Chinese section and a Muslim section. Chinese, Indians, and later on Japanese and Persians all settled in Ayutthaya, the Thai kings welcoming their presence and granting them complete freedom of worship. Several of these foreigners became important cour t officials.
Containing merchandise from all corners of Asia, the thriving markets of Ayutthaya attracted traders from Europe. The Portuguese were the first to arrive, in 1511, at the time when Albuquerque was attempting to conquer Melaka (Malacca). They conclu ded their first treaty with Ayutthaya in 1516, receiving permission to settle in Ayutthaya and other Thai ports in return for supplying guns and ammunition to the Thai king. Portugal's powerful neighbor Spain was the next European nation to arrive in Ayutthaya, towards the end of the 16th century. The early 17th century saw the arrival of two northern European East India Companies: The Du tch (V.O.C) and the British. The Dutch East India Company played a vital role in Ayutthaya's foreign trade from 1605 until 1765, succeeding in obtaining from the Thai kings a deerhide export monopoly as well as one of all the tin sold at Nakhon Si Thammarat. The Dutch sold Thai sapanwood and deerhides for good profits in Japan during Japan's exclusion period, after 1635.
The French first arrived in 1662, during the reign of Ayutthaya's most outward-looking and cosmopolitan ruler, King Narai (1656-1688). French missionaries and merchants came to the capital, and during the 1680's splendid embassies were exchanged between King Narai and King Louis XIV. The French tried to convert King Narai to Christianity and also attempted to gain a foothold in the Thai kingdom when, in 1687, they sent troops to garrison Bangkok and Mergui. When a succession conflict broke out in 1688 an anti-French official seized power, drove out the French garrisons, and executed King Narai's Greek favorite Constantine Phaulkon, who had bee championing the French cause. After 1688, Ayutthaya had less cont act with Western nations, but there was no policy of national exclusion. Indeed, there was increased trading contact with China after 1683,and there was continued trade with the Dutch, the Indians, and various neighbouring countries.
Ayutthaya's relations with its neighbours were not always cordial. Wars were fought against Cambodia, Lanna, Lanchang (Laos), Pattani, and above all, Burma, Ayutthaya's powerful neighbour to the west. Burmese power waxed an d waned in cycles according to their administrative efficiency in the control of manpower. Whenever Burma was in an expansionist phase, Ayutthaya suffered. In 1569, King Bayinnaung captured Ayutthaya, thus initiating over a decade's subjection to the Burmese. One of the greatest Thai military leaders, Prince (later King) Naresuan, then emerged to declare Ayutthaya's independence and to defeat the Burmese in several battles and skirmishes, culminating in the victory of Nong Sarai, when he killed the Burmese Crown Prince in combat on elephant back.
Thonburi was founded by a Thai general named Phraya Taksin, who was later crowned King Taksin Maharaj. After the fall of Ayutthaya to the Burmese in 1767, Thonburi, situated on the west bank of the Chao Phraya opposite what is now the City of Bangkok, became the new Thai capital.
After the shattering defeat which had culminated in Ayutthaya's destruction, the death and capture of thousands of Thais by the victorious Burmese, and the dispersal of several potential Thai leaders, the situation seemed hopeless. It was a time of darkness and of troubles for the Thai nation. Members of the old royal family of Ayutthaya had died, escaped, or been captured by the Burmese and many rival claimants for the throne emerged, based in different areas of the country. But out of this national catastrophe emerged yet another saviour of the Thai state - the half-Chinese general Phraya Taksin, former governor of Tak. Within a few years this determined warrior had defeated not only all his rivals but also the Burmese invaders and had set himself up as king,
Since Ayutthaya had been so completely devastated. King Taksin chose to establish his capital at ThonBuri [ across the river from Bangkok ]. Although a small town, ThonBuri was strategically situated near the mouth of the Chao Phraya River and therefore suitable as a seaport. The Thais needed weapons, and one way of acquiring them was through trade. Besides, foreign trade was also needed to bolster the Thai economy, which had suffered extensively during the war with Burma (now Myanmar). Chinese and Chinese-Thai traders helped revive the economy by engaging in maritime trade with neighboring states, with China, and with some European nations.
King Taksin's prowess as a general and as an inspirational leader meant that all attempts by the Burmese to re-conquer Siam failed. The rallying of the Thai nation during a time of crisis was King Taksin's greatest achievement. However, he was also interested in cultural revival, in literature and the arts. He was deeply religious and studied meditation to an advanced level. The stress and strain of such much fighting and the responsibility of rebuilding a centralized Thai state took their toll on the king. Following an internal political conflict in 1782. King Taksin's fellow general Chao Phraya Chakri was chosen king. King Taksin's achievements have caused to bestow on him the epithet "The Great".
The Chakris were inaugurated on April 6, 1782 together with the coronation of Rama I or King Buddha Yot Fa Chulalok. He moved the capital across the Chao Phaya River from Thonburi to a small village known as "Bangkok" and raised up new laws to rule the country. Under his reign, Thailand covered all areas of present day Laos and parts of Burma, Cambodia and Kedah province in Malaysia.
In 1809, Rama II or King Buddha Loet Lad, son of Rama I took the throne until 1824. He devoted himself to preserve the Thai literature that had remained from Ayutthaya period and produced a new version of Ramakien or Thai Ramayana, the classical literature.
In 1824-1851, Rama III or King Nang Klao was successful in re-establishing relation and making trades with China which was necessary to meet the increasing domestic agricultural production.
Rama IV or King Mongkut (Phra Chom Klao), who reigned from 1851 to 1868 lived as a Buddhist monk for 27 years. During his monastic period, he could speak many languages such as Latin, English, and five other languages. He also studied western sciences and adopted the discipline of local Mon monk. Under his reign, he created new laws to improve the women's and children's right, opened new waterways and roads, and created the first printing press.
Rama V or King Chulalongkorn, Rama IV's son, continued the throne from 1868 to 1910. He started to reform the tradition, legal and administrative realm by allowing officials to sit on chairs during royal audiences. Under the reign of Rama V, Thailand developed relations with European nations and the USA. He introduced schools, roads, railways, and Thailand's first post office. He even established civil service system. In 1892, Rama V overhauled the administration of Siam to a form of cabinet government with 12 ministers.
In 1886, Siam lost some territory to French, Laos and British Burma accorded the foreign powers intercede. After that King Chulalongkorn declared Thailand as an independent kingdom on the 23rd of October, making this day as a national holiday. Every year this national holiday is celebrated in commemoration of this event and people lay wreaths in memory of king they called "Phra Piya Maharaj"
Rama VI or King Vajiravudh, took the throne from 1910 to 1925. During his short reign, he introduced the westernization to Thailand. He introduced the primary school education, Thai women were encouraged to grow their hair at a certain length. Surnames were introduced, and football was introduced in Thailand.
1925-1935 was the period of Rama VII or King Prachadhipok, Rama VI's brother. He changed Siam's form of government from absolute monarchy to democracy. This revolution developed the constitutional monarchy along British lines, with mixed military and civilian group in power. At that time, Phibul Songkhram was a key military leader in the 1932 coup. He maintained his position and power from 1938 until the end of World War II.
Rama VIII or King Ananda Mahidol, a nephew of Rama VII, took the throne in 1935 but was assassinated under mysterious circumstances in 1946. His brother King Bhumipol Aduldej succeeded as Rama IX.
Under Rama IX's government, the country's name was officially changed from "Siam" to "Thailand" in 1946 which was defined in Thai as "Prathet Thai", the word "Prathet" means "country" and the word "Thai" means "free" referring to the Thai races.