[4] "Kra–Dai" has since been used by the majority of specialists working on Southeast Asian linguistics, including Norquest (2007),[5] Pittayaporn (2009),[6][7] Baxter & Sagart (2014),[8] and Enfield & Comrie (2015).

[13] James R. Chamberlain (2016) 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 fiefdom and the beginning of the Zhou dynasty.

Weera Ostapirat (2005) sets out a series of regular sound correspondences between them, assuming a model of a primary split between the two; they would then be co-ordinate branches.

[18] On the other hand, Laurent Sagart (2008) proposes that Kra–Dai is a later form of what he calls "FATK" (Formosan Ancestor of Tai–Kadai) a branch of Austronesian belonging to the subgroup "Puluqic", developed in Taiwan, whose speakers migrated back to the mainland, to Guangdong, Hainan, and north Vietnam, around the second half of the 3rd millennium BCE.

[19] Upon their arrival in this region, they underwent linguistic contact with an unknown population, resulting in a partial relexification of FATK[a] vocabulary.

[20] Erica Brindley (2015) supports Sagart's hypothesis, arguing that the radically different Kra-Dai history of migration to the mainland (as opposed to the Philippines for Proto-Austronesian) and extended contact with Austro-Asiatic and Sinitic speakers would make the relationship appear more distant.

[21] Besides various concrete pieces of evidence for a Kra–Dai existence in present-day Guangdong, remnants of Kra–Dai languages spoken further north can be found in unearthed inscriptional materials and non-Han substrata in Min and Wu Chinese.

[citation needed] Wolfgang Behr (2002, 2006, 2009, 2017)[22][23][24] points out that most non-Sinitic words found in Chu inscriptional materials are of Kra–Dai origin.

< OC *nnəŋ) in the E jun qijie 鄂君啟筯 bronze tally and in Warring States bamboo inscriptions, which represents a Kra–Dai areal word; compare Proto-Tai *hnïŋ = *hnɯŋ (Siamese 22nɯŋ, Dai 33nɯŋ, Longzhou nəəŋA etc.)

[27] Later, Zhengzhang Shangfang (1991) followed Wei's proposal but used Thai script for comparison, since this orthography dates from the 13th century and preserves archaisms not found in modern pronunciation.

However, Western scholars generally consider them to be Sinitic loanwords and note that basic vocabulary words in Kra–Dai languages often have cognates with Austronesian instead.

He further suggests that similarities between Kra–Dai and Austronesian are due to later areal contact in the coastal areas of eastern and southeastern China or an older ancestral relation (Proto-East Asian).