Short answers, pulled from the story.
The Sukhothai Kingdom began in 1238 when a coalition of Siamese forces led by Bang Klang Hao recaptured the city. The kingdom ended in 1438 when Borommarachathirat II of Ayutthaya installed his son Ramesuan as Upparat, marking the loss of independence.
Bang Klang Hao led the coalition that re-established Sukhothai as an autonomous polity in 1238. Ram Khamhaeng the Great later expanded the kingdom beyond its original borders through military conquest and diplomatic alliances.
The Ram Khamhaeng Inscription serves as the primary historical record discovered by Mongkut nearly six centuries after it was created. It details the administrative system, heroic kings like Ram Khamhaeng, and provides direct evidence from the period rather than relying on later chronicles.
Sukhothai established diplomatic relations with Yuan China by sending trade missions that exported sangkhalok ware. This ceramic style represents the only period in Thai history where Siam produced Chinese-style ceramics before production ceased entirely by the fourteenth century.
Tributary states began to break away rapidly after the death of Ram Khamhaeng in 1298 when far-flung bonds of vassalage disintegrated. The kingdom officially lost independence in 1438 when Ayutthaya installed a viceroy and military garrison in Sukhothai.