Prior to the 13th century, Tai kingdoms had existed on the northern highlands including the Ngoenyang (centered on Chiang Saen; predecessor of Lanna) 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 stated 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 (now a part of Sukhothai Province as Amphoe). Sukhothai had enjoyed a substantial autonomy until it was re-conquered around 1180 by the Mons of Lawo under