Comparative linguistic research seems to indicate that the Tai peoples were a Proto-Tai–Kadai speaking culture of southern China and dispersed into to mainland Southeast Asia. Many of linguists proposes that Tai–Kadai peoples may genetically connected with Proto-Austronesian speaking peoples, Laurent Sagart (2004) hypothesized that the Tai–Kadai peoples may originally have been of Austronesian descent. Prior to living in mainland China, Tai-Kadai peoples are thought to have migrated from a homeland on the island of Taiwan, where they spoke a dialect of Proto-Austronesian or one of its descendant languages.^[19] Unlike the Malayo-Polynesian group who later sailed south to the Philippines and other parts of maritime Southeast Asia, the ancestors of the modern Tai-Kadai people sailed west to mainland China and possibly traveled along the Pearl River, where their language greatly changed from other Austronesian languages under the influence of Sino-Tibetan and Hmong–Mien language infusion.^[20] Aside from linguistic evidence, the connection between Austronesian and Tai-Kadai can also be found in some common cultural practices. Roger Blench (2008) demonstrates that dental evulsion, face tattooing, teeth blackening and snake cults are shared between the Taiwanese Austronesians and the Tai-Kadai peoples of Southern China.^[21]

James R. Chamberlain proposes that the Tai-Kadai (Kra-Dai) language family was formed as early as the 12th century BCE in the middle of the Yangtze basin, coinciding roughly with the establishment of the Chu state and the beginning of the Zhou dynasty. Following the southward migrations of Kra and Hlai (Rei/Li) peoples around the 8th century BCE, the Yue (Be-Tai people) started to break away and move to the east coast in the present-day Zhejiang province, in the 6th century BCE, forming the state of Yue and conquering the state of Wu shortly thereafter. According to Chamberlain, Yue people (Be-Tai) began to migrate southwards along the east coast of China to what are now Guangxi, Guizhou and northern Vietnam, after Yue was conquered by Chu around 333 BCE. There the Yue (Be-Tai) formed the Luo Yue, which moved into Lingnan and Annam and then westward into northeastern Laos and Si p Song Chau Tai, and later became the Central-Southwestern Tai, followed by the Xi Ou, which became the Northern Tai.^[22]