Based on some cultural, ritual, and linguistic evidence I've seen, I think Ba, Chu, Wu, and Yue may have been part of an early Kra-Dai speaking continuum. The Tai, Kam-Sui, Kra, and Hlai peoples can be viewed as surviving branches of a broader early Kra-Dai tradition that once stretched across the Yangtze region. These early Kra-Dai populations likely contributed to both the Southern Han and modern Kra-Dai speaking peoples.
Hmong-Mien groups were likely present in Chu and Wu, but they appear to have been concentrated more in the highlands. One reason is that Hmong-Mien languages do not preserve the same extensive Old Chinese layer found throughout Kam-Tai languages. Since Chu began as a Zhou vassal state, we would expect stronger traces of early Zhou influence if Hmong-Mien groups formed its core population. Kam-Tai languages preserve a much deeper Old Chinese layer alongside cultural parallels with Chu and Zhou.
Some Kam-Tai groups preserve pre-Han calendars, Zhou-era customs, and ritual traditions that parallel those of Chu. Variants of rituals such as Zhaohun 招魂 (soul-calling), the Wu 巫 (Mo) shamanic tradition, and aspects of Sheji 社稷 style agricultural and territorial rituals remain important in Tai religious and community life in Laos, Northern Thailand, Xishuangbanna, and neighboring regions.
When examining the non-Sinitic words recorded as "Chu dialect" in Chu sources, a significant number appear to have convincing Kra-Dai parallels. This does not prove that every aspect of Chu was Kra-Dai, but taken together, the linguistic, ritual, and cultural evidence points to a strong Kra-Dai foundation in the Chu-Wu-Yue world.
Some Chinese scholars argue that the Chu royal surname 芈, written by Chu people themselves as 嬭 in bronze inscriptions, originally meant "mother." Later sources such as the Qieyun state that 嬭 was the Chu word for "mother." Similar forms survive today in Wu, Min, Hakka, and She dialects, and Ye Yanpeng (2025) argues they correspond closely to Proto-Tai *meeC "mother" in both sound and tone category. If correct, the Chu clan name may preserve traces of an older southern maternal tradition.
Possible Kra-Dai Parallels in Chu Ritual Vocabulary
Zhaohun 招魂 (Calling Back the Soul)
Old Chinese: *tjew qʷˤən
Comparable Tai forms:
Northern Thai: ju khwan
Lao: su khwan
Wu 巫 (Shaman, Ritual Specialist, Healer)
Old Chinese: *ma / *mro
Comparable Tai forms:
Proto-Tai: *mo
Lao: mo
Northern Thai: mo
It's very likely the Tanka trace back to the Dan (蜑 / 巴蜑 / 夷蜑) groups of the Ba region. Historical records place them in Chongqing, western Hubei, and the Three Gorges, living on boats sailing up and down the Yangtze. Some sources say parts the Dan made up the ruling elite of Ba. They are also grouped under labels like Man (蛮) and Liao (僚), which are tied to Kra-Dai populations, particularly the Kra branch.