HMONG-MIEN
Hmong-Mien is clearly split into two coherent branches, namely Hmongic and Mienic.
Selected words are available in:
Hsiu, Andrew. 2017. Mienic lexical isogloss database. m.s.
Hmongic branch
Mienic branch
HISTORY
Based on geographic and linguistic evidence, my hypothesis is that Proto-Hmong-Mien was spoken around Lake Dongting in the Xiang River drainage basin region just south of the Yangtze River in Hunan province, China, about 2,500 years B.P. Rice agriculture and Chinese technology from the Yellow River Valley were the most likely major factors motivating Hmong-Mien dispersal. The current distribution of Hmong-Mien sub-branches suggests that the dispersal had occurred from downstream to upstream via riverine routes (Map 1).
I consider Shehua to be the "third" missing branch of Hmong-Mien spoken in Jiangxi province. Shehua has been relexified by early forms of Hakka, perhaps sometime around the Tang dynasty. You (2002) has identified various Shehua words of non-Sinitic origin. I have analyzed these words and found that they have various parallels with divergent Hmong-Mien languages such as Pa-Hng, Qo Xiong, Dzao Min, Jiongnai, She, Bana, and others. Although these words of clearly of Hmong-Mien origin, the lack of any clear connection with any single Hmong-Mien language suggests that the substratum of Shehua represents a third branch of Hmong-Mien.
Map 1: Proposed dispersal of the Hmong-Mien language family, with branches labeled in red. Synchronic languages are labeled in purple.
References
You Wenliang 游文良. 2002. Shezu yuyan 畲族语言. Fuzhou: Fujian People's Press 福建人民出版社. ISBN 7-211-03885-3