Rise of Southward-Migrating Thai Forces

Timeline

1. 1221–1226Shan Plateau · MyanmarThe decline of the Dali Kingdom and conflicts among neighboring polities drove Tai-speaking groups south along the Lancang-Mekong-Salween corridors. Migrants organized into chiefly polities, gradually breaking free from their former overlords and establishing autonomous settlements in mountain valleys.
2. 1227–1229Sukhothai region · ThailandThai chiefly powers expanded across the upper Chao Phraya plains as local Mon and Khmer frontier control weakened. Several city-states held strategic points, controlling irrigation and the salt and iron trade, forming the embryo of the later Sukhothai Kingdom.
3. 1228–1230Northern Indochinese Peninsula · MyanmarThai southward migration altered the peninsula's ethnic and linguistic distribution, compounding the decline of old empires like Angkor and Bagan. By 1230, Thai-speaking peoples had formed political units in multiple river valleys, opening the way for Thai states to gain independence and challenge Khmer and Mon rule in the mid-to-late 13th century.