Binciken harshe na kwatankwacin yana nuna cewa al'ummar Tai al'adun Proto-Tai-Kadai ne na kudancin kasar Sin kuma sun watsu zuwa yankin kudu maso gabashin Asiya.Yawancin masana harsuna suna ba da shawarar cewa mutanen Tai-Kadai na iya danganta su ta asali da mutanen Proto-Austronesia, Laurent Sagart (2004) ya yi hasashen cewa mutanen Tai-Kadai na iya kasancewa asalin asalin Austronesia ne.Kafin zama a babban yankin kasar Sin, ana tunanin al'ummar Tai-Kadai sun yi hijira daga kasarsu ta tsibirin Taiwan , inda suke magana da yare na Proto-Austronesia ko kuma daya daga cikin yarensa.^[19] Ba kamar ƙungiyar Malayo-Polynesian waɗanda daga baya suka tashi zuwa kudu zuwa Philippines da sauran sassan tekun kudu maso gabashin Asiya, kakannin mutanen Tai-Kadai na zamani sun yi tafiya zuwa yamma zuwa babban yankin kasar Sin kuma mai yiwuwa sun yi tafiya tare da kogin Pearl, inda harshensu ya yi yawa. canza daga sauran harsunan Australiya a ƙarƙashin tasirin jiko na Sino-Tibet da Hmong-Mien.^[20] Baya ga shaidar harshe, ana iya samun alaƙa tsakanin Austronesia da Tai-Kadai a cikin wasu al'adu na gama gari.Roger Blench (2008) ya nuna cewa ficewar haƙora, yin tattoo fuska, baƙar hakora da ƙungiyoyin macizai suna da alaƙa tsakanin mutanen Austronesians na Taiwan da mutanen Tai-Kadai na Kudancin China.^[21]James R. Chamberlain ya ba da shawarar cewa an kafa dangin harshen Tai-Kadai (Kra-Dai) a farkon karni na 12 KZ a tsakiyar tafkin Yangtze, wanda ya yi daidai da kafuwarkasar Chu da farkon daular Zhou. .Bayan hijira zuwa kudu na mutanen Kra da Hlai (Rei/Li) a cikin karni na 8 KZ, Yue ('yan kabilar Be-Tai) sun fara watsewa zuwa gabar tekun gabas a lardin Zhejiang na yanzu, a karni na 6. BC, kafa jihar Yue da kuma mamaye jihar Wu jim kadan bayan haka.A cewar Chamberlain, mutanen Yue (Be-Tai) sun fara yin ƙaura zuwa kudu tare da gabashin gabar tekun China zuwa yankin Guangxi da Guizhou da arewacin Vietnam , bayan da Chu ta ci Yue a shekara ta 333 KZ.A can ne Yue (Be-Tai) suka kafa Luo Yue, wanda ya koma Lingnan da Annam sannan ya koma yamma zuwa arewa maso gabashin Laos da Sip Song Chau Tai, daga baya kuma ya zama Tai ta tsakiya da kudu maso yammacin kasar, sai Xi Ou, wanda ya zama Arewacin Tai.^[22]