The forebears of the modern Thai were Tai-speaking people living south of the Chang Jiang (Yangtze River) on the mountainous plateau of what is now the Chinese province of Yunnan (see The Thai and Other Tai-Speaking Peoples , ch. 2). Early Chinese records (the first recorded Chinese reference to the Tai is dated sixth century B.C.) document the Tai cultivating wetland rice in valley and lowland areas. During the first millennium A.D., before the emergence of formal states governed by Taispeaking elites, these people lived in scattered villages drawn together into muang, or principalities. Each muang was governed by a chao, or lord, who ruled by virtue of personal qualities and a network of patron-client relationships. Often the constituent villages of a muang would band together to defend their lands from more powerful neighboring peoples, such as the Chinese and Vietnamese.

The state of Nanchao played a key role in Tai development. In the mid-seventh century A.D., the Chinese Tang Dynasty, threatened by powerful western neighbors like Tibet, sought to secure its southwestern borders by fostering the growth of a friendly state formed by the people they called man (southern barbarians) in the Yunnan region. This state was known as Nanchao. Originally an ally, Nanchao became a powerful foe of the Chinese in subsequent centuries and extended its domain into what is now Burma and northern Vietnam. In 1253 the armies of Kublai Khan conquered Nanchao and incorporated it into the Yuan (Mongol) Chinese empire.

Nanchao's significance for the Tai people was twofold. First, it blocked Chinese influence from the north for many centuries. Had Nanchao not existed, the Tai, like most of the originally non-Chinese peoples south of the Chang Jiang, might have been completely assimilated into the Chinese cultural sphere. Second, Nanchao stimulated Tai migration and expansion. Over several centuries, bands of Tai from Yunnan moved steadily into Southeast Asia, and by the thirteenth century they had reached as far west as Assam (in present-day India). Once settled, they became identified in Burma as the Shan and in the upper Mekong region as the Lao. In Tonkin and Annam, the northern and central portions of present-day Vietnam, the Tai formed distinct tribal groupings: Tai Dam (Black Tai), Tai Deng (Red Tai), Tai Khao (White Tai), and Nung. However, most of the Tai settled on the northern and western fringes of the Khmer Empire.

The Thai have traditionally regarded the founding of the kingdom of Sukhothai as marking their emergence as a distinct nation. Tradition sets 1238 as the date when Tai chieftains overthrew the Khmer at Sukhothai, capital of Angkor's outlying northwestern province, and established a Tai kingdom. A flood of migration resulting from Kublai Khan's conquest of Nanchao furthered the consolidation of independent Tai states. Tai warriors, fleeing the Mongol invaders, reinforced Sukhothai against the Khmer, ensuring its supremacy in the central plain. In the north, other Tai war parties conquered the old Mon state of Haripunjaya and in 1296 founded the kingdom of Lan Na with its capital at Chiang Mai (see fig. 4).

Data as of September 1987