Khmer Era

Originally, Sukhothai was a Khmer empire's outpost named Sukhodaya.[1][2][3] During the reign of Khmer Empire, the Khmers built some monuments there, several of them survived in Sukhothai Historical Park such as the Ta Pha Daeng shrine, Wat Phra Phai Luang, and Wat Sisawai.[4] About some 50 kilometer north of Sukhothai is another Khmer military outpost of Si Satchanalai or Sri Sajanalaya.[5][6]

In the mid-13th century, the Tai tribes led by Si Indradit rebelled against the Khmer governor at Sukhodaya and established Sukhothai as an independent Tai state and remained the center of Tai power until the end of the fourteenth century.[1][6]

Liberation from Khmer Empire (Lavo)  Zones of influence of Sukhothai and its neighbours, c. 1300

Prior to the 13th century, a succession of Tai kingdoms existed in the northern highlands including the Ngoenyang (centered on Chiang Saen, predecessor of Lan Na) kingdom and the Heokam (centered on Chiang Hung, modern Jinghong in China) kingdom of Tai Lue people. Sukhothai had been a trade center and part of Lawo, which was under the domination of the Khmer Empire. The migration of Tai people into the upper Chao Phraya valley was somewhat gradual.

Modern historians believe that the secession of Sukhothai (once known as Sukhodaya) from the Khmer empire began as early as 1180 during the reign of Pho Khun Sri Naw Namthom who was the ruler of Sukhothai and the peripheral city of Sri Satchanalai (modern day Si Satchanalai District in Sukhothai Province). Sukhothai had enjoyed substantial autonomy until it was re-conquered around 1180 by the Mons of Lawo under Khomsabad Khlonlampong.

Two brothers, Pho Khun Bangklanghao and Pho Khun Phameung took Sukhothai from Mon hands in 1239. Khun (ขุน) before becoming a Thai feudal title, was a Tai title for a ruler of a fortified town and its surrounding villages, together called a muang; in older usage prefixed pho (พ่อ) 'father',[7] Comparable in sound and meaning to rural English 'paw'. Bangklanghao ruled Sukhothai as Sri Indraditya and began the Phra Ruang dynasty. He expanded his kingdom to bordering cities. At the end of his reign in 1257, the Sukhothai Kingdom covered the entire upper valley of the Chao Phraya River (then known simply as Menam, 'mother of waters', the generic Thai name for rivers.)

Traditional Thai historians considered the founding of the Sukhothai Kingdom as the beginning of the Thai nation because little was known about the kingdoms prior to Sukhothai. Modern historical studies demonstrate that Thai history began before Sukhothai. Yet the foundation of Sukhothai is still a celebrated event.

Expansions under Ramkamhaeng  Inscription stele of King Ram Kamhaeng the Great

Pho Khun Ban Muang and his brother Ram Khamhaeng expanded the Sukhothai Kingdom. To the south, Ramkamhaeng subjugated the kingdoms of Supannabhum and Sri Thamnakorn (Tambralinga) and, through Tambralinga, adopted Theravada as the state religion. To the north, Ramkamhaeng put Phrae and Muang Sua (Luang Prabang) under tribute.

To the west, Ramkhamhaeng helped the Mons under Wareru (who is said to have eloped with Ramkamhaeng's daughter) to free themselves from Pagan domination and establish a kingdom at Martaban (they later moved to Pegu). So, Thai historians considered the Kingdom of Martaban a Sukhothai tributary. In practice, Sukhothai domination may not have extended that far.

With regard to culture, Ramkhamhaeng had the monks from Sri Thamnakorn propagate the Theravada religion in Sukhothai. In 1283, Ramkamhaeng is said to have invented Thai script, incorporating it into the controversial Ramkamhaeng Stele discovered by Mongkut 600 years later.

It was also during this period that the first contacts with Yuan dynasty were established and Sukhothai began sending trade missions to China. One well-known export of Sukhothai was the Sangkalok (Song dynasty pottery). This was the only period that Siam produced Chinese-styled ceramics, which fell out of use by the 14th century.

Decline and domination of Ayutthaya

Sukhothai domination was short-lived. After the death of Ramkhamhaeng in 1298, Sukhothai's tributaries broke away. Ramkhamhaeng was succeeded by his son, Loe Thai. The vassal kingdoms, first Uttaradit in the north, then soon after the Laotian kingdoms of Luang Prabang and Vientiane (Wiangchan), liberated themselves. In 1319 the Mon state to the west broke away, and in 1321 the Lanna absorbed Tak, one of the oldest towns under the control of Sukhothai. To the south, the powerful city of Suphanburi also broke free early in the reign of Loe Thai. Thus the kingdom was quickly reduced to its former local importance only. Finally in 1378, the armies of the expanding Ayutthaya Kingdom invaded and forced Sukhothai's King Thammaracha II to yield to this new power. After the Battle of Sittaung River in 1583, King Naresuan of Phitsanulok (and crown prince of Ayutthaya) forcibly relocated people from Sukhothai and surrounding areas to the Southern Central plain,[8] due to the war with the Burmese and an earthquake.

Later Development  Crown prince Vajiravudh conducted archaeological research at Sukhothai in 1907

Sukhothai repopulated again but declined due to successive Burmese–Siamese wars, especially the Burmese–Siamese War (1765–67). In 1793 Rama I, after establishing Bangkok as a new capital city of the kingdom, founded New Sukhothai in Thani, 12 km (7.5 mi) to the east of old Sukhothai, thus abandoning Sukhothai. In 1801 Rama I commissioned the construction of many royal temples in the capital city. He ordered that old Buddha images be brought to Bangkok from the ruined temples around the country. One of the Buddha images is the famous eight metre (25 foot) tall bronze Phra Sri Sakyamuni (Thai: พระศรีศากยมุนี; RTGS: phra si sakkayamuni), the principal Buddha image of Wat Suthat, which was the principal Buddha image of Wat Mahathat, the biggest temple in Sukhothai. In 1833 Mongkut, during his monkhood, travelled to Sukhothai and discovered the controversial Ramkhamhaeng stele in Wat Mahathat and other artifacts, now in the National Museum in Bangkok. The formal name of this stone is The King Ram Khamhaeng Inscription Documentary heritage inscribed on the Memory of the World Register in 2003 by UNESCO.

In 1907, Vajiravudh, as crown prince, conducted a two-month archaeological field trip to Nakhon Sawan, Kampheang Phet, Sukhothai, Si Satchanalai, Uttaradit, and Pitsanulok. He later published "Phra Ruang City Journey" (Thai: เที่ยวเมืองพระร่วง; RTGS: Thiao Muang Phra Ruang) to promote historical and archaeological study by the public. The work has been used by later archaeologists and historians including Damrong Rajanubhab, the founder of the modern Thai educational system and George Coedès, a 20th-century scholar of southeast Asian archaeology and history.

In July 1988 the historical park was officially opened. On 12 December 1991, it was declared a World Heritage Site as part of the Historic Town of Sukhothai and Associated Historic Towns together with the associated historical parks in Kamphaeng Phet and Si Satchanalai.