The Sukhothai kingdom was an early kingdom in the area around the city Sukhothai, in north central Thailand. It existed from 1238 till 1438. The old capital, now 12 km outside of New Sukhothai in Tambon Mueang Kao, is in ruins and is a historical park.
Chiang Saen was established in the early 700s and Mueang Sua (Luang Prabang) around AD 728 making them the first kingdoms established by the Tai-speaking people in southeast Asia, prior to the migration and expansion of the Tai-speaking people into northern Thailand, Laos, and eventually into central Thailand and central Laos.
The city of Sukhotai was part of the Khmer empire until 1238, when two Thai chieftains, Pho Khun Pha Muang and Pho Khun Bang Klang Hao, declared their independence and established a Thai-ruled kingdom. Pho Khun Bang Klang Hao later became the first king of Sukhotai, calling himself Pho Khun Si Indrathit (or Intradit). This event traditionally marks the founding of the modern Thai nation, although other less well-known Thai kingdoms, such as Lanna, Phayao and Chiang Saen, were established around the same time.
Sukhotai expanded by forming alliances with the other Thai kingdoms, adopting Theravada Buddhism as the state religion with the help of Ceylonese monks. Intradit was succeeded by his son Pho Khun Ban Muang, who was followed in 1278 by his brother, Pho Khun Ramkhamhaeng. Under King Ramkhamhaeng the Great, as he is now known, Suriyothai enjoyed a golden age of prosperity. Ramkhamhaeng is credited with designing the Thai alphabet (traditionally dated from 1283, on the evidence of the controversial Ramkhamhaeng stele, an inscribed stone allegedly bearing the earliest known Thai writing). At its peak, supposedly stretching from Martaban (now in Burma) to Luang Prabang (now in Laos) and down the Malay Peninsula as far south as Nakhon Sri Thammarat, the kingdom's sphere of influence was larger than that of modern Thailand, although the degree of control exercised over outlying areas was variable.
After Ramkhamhaeng's death, he was succeeded by his son Loethai. The vassal kingdoms, first Uttaradit in the north, then soon after the Laotian kingdoms of Luang Prabang and Vientiane (Wiangchan), liberated themselves from their overlord. In 1319 the Mon state to the west broke away, and in 1321 Lanna placed Tak, one of the oldest towns under the control of Suriyothai, under its control. To the south the powerful city of Suphanburi also broke free early in the reign of Loethai. Thus the kingdom was quickly reduced to its former local importance only. Meanwhile, Ayutthaya rose in strength, and finally in 1378 King Thammaracha II had to submit to this new power.
The Silajaruek Sukhotai are hundreds of stone inscriptions that form a historical record of the period. Among the most important inscriptions are Silajaruek Pho Khun Ramkamhaeng (Stone Inscription of King Ramkamhaeng), Silajaruek Wat Srichum (an account on history of the region itself and of Srilanka), and Silajaruek Wat Pamamuang (a Politico-Religious record of King Loethai).
Sukhotai became a tributary state of Ayutthaya between 1365 and 1378. In 1412 Ayutthaya installed a chief resident, and King Thammaracha IV was installed on the throne by Ayutthaya. Around 1430 Thammaracha moved his capital to Phitsanulok, and after his death in 1438 the kingdom was reduced in status to a mere province of Ayutthaya.