I'm not sure if the following is the best way to begin. It seems like I'm taking too long to get to the central points of my dissertation.
The starting point for my dissertation was the discovery by a Japanese anthropoligical team, led by Shiratori Yoshiro, of ritual manuals and other materials, written in a variant of classical Chinese, in Yao/Mien villages in Northern Thailand. Shiratori's published collection of reproductions of these materials, known as the Yao Documents (1975) caused an international stir among sinologists, anthropologists, and historians, in that it seemed to indicate that a non-Chinese (non-Han) group living in the mountains of Northern Thailand were using Chinese texts in their religious practice. In1982, Michel Strickmann, a sinologist and specialist on religious Daoism, published a brief article, entitled, "The Tao Among the Yao: Taoism and the Sinification of South China," which argued that the materials collected by Shiratori had more affinities with Chinese religion than simply the script in which they were written; the majority were Daoist ritual manuals. In the same year, a French ethnographer, named Jacques Lemoine, published a full length manuscript, called, Yao Ceremonial Paintings, which followed Strickmann in maintaining that the deities represented in Yao paintings were Daoist in origin, and that the bulk of their culture--their writing system, their cosmology, their festivals, their rituals--were borrowed from the dominant Han Chinese.
It should not seem strange that there are affinities between Yao and Chinese culture, because Yao in Thailand migrated there from Central and South China (Hunan, Guangxi, Guangdong, and Yunnan), where they still reside.