This theory was first proposed (made) in 1885 by Terrien de la Couperie, who was a French linguist (someone who studies languages). He said that Thai people were the ancestors of the Ta Mung people of southern China, in an old kingdom called Nanchao, which was located in present day Yunnan. While he may have been the first person to propose this theory, later historians also believed that the ancestors of Tai people came from this region.

In 1951, M. Carthew, like de la Couperie, claimed that the Tai people came from Yunnan. His sources however, were questionable. He claimed that a Chinese historian named Yang-Tsai wrote a history book about southern China in 1537. In his book, Yang-Tsai said that the Tais lived in what is now the province of Yunnan. This book was apparently translated into English in 1894 by a man named G. W. Clark. Neither Yang-Tsai’s original Chinese language history book, nor Clark’s English language version are available to the public. Apparently only four copies of Clark’s book exist, but they are in a private collection (they are all owned by one person). Therefore, Carthew’s claims about the origins of Tai people are not very trustworthy. Although these European historians did not use good sources to make their arguments, their books were very influential (many people read them and believed them).

Another influential person who supported this theory was Prince Damrong. He was the son of King Rama 4 and brother of King Rama 5, and he was considered “the father of modern Thai history.” He believed that the original homeland of Tai people was situated near Tibet. After they were attacked by the Chinese, according to Damrong, the Tai people had to move and settle in Nanchoa. They were later attacked by the Mongolian emperor Kublai Khan in 1234, and had to move further south to modern day Thailand.

This theory is considered invalid (not true) today. There is no real primary evidence to support the theory that Thai people came from Nanchao. As one historian points out, there is no evidence that people ever spoke the Tai language as far North as Yunnan. Also, the way that the Nanchoa people named their kings is nothing like the way Thai people named their kings. Therefore, we need to consider other theories if we want to learn the truth about Thai origins.