Several macrofamily schemes have been proposed for linking multiple language families of Southeast Asia. None of these proposals is yet accepted by mainstream comparative linguistics, though research into higher-level relationships among these languages has gained some renewed scholarly interest over the last three decades; the various hypotheses are still under investigation, and the validity of each has yet to be resolved.
Austro-Tai links the Austronesian and Kra–Dai languages. Several current scholars, including Laurent Sagart, Stanley Starosta, Weera Ostapirat and Lawrence Reid, accept or theorize a close relationship between these families, but the specifics of the relationship remain unclear. Multiple models of the internal branching of Austro-Tai have been put forward, and Austro-Tai has been incorporated as a subgroup within some larger macrofamily schemes, e.g. in Starosta's East Asian as well as in Sagart's model of Austronesian, both of which regard Kra–Dai as a subfamily within Austronesian. A few versions of Austro-Tai have included Japonic and/or the isolate Ainu as well, though these have not been met with as much acceptance.
Miao–Dai is a hypothesis for a family including Miao–Yao and Kra–Dai.
Austric links all of the major language families of Southeast Asia apart from Sino-Tibetan. Several variants of the Austric hypothesis have been proposed since it took shape with Paul K. Benedict's proposal. Some of these also incorporate Japonic, Korean and/or Ainu. One version called the "Greater Austric" hypothesis includes Ainu as well as Nihali, a language isolate of India.
* The "Proto-Asian hypothesis" or "Austro-Asian" argues for lexical evidence of relationship among all of the languages typically included in Austric as well as Japanese–Korean and Sino-Tibetan.
East Asian covers all of these families as well as Sino-Tibetan. It posits Austronesian as the most divergent branch, coordinate with a primary branch Sino-Tibetan–Yangzian which links Sino-Tibetan with a clade called Yangzian, named for the Yangtze river, which includes Austroasiatic and Hmong–Mien.
In a different direction, the Dené–Caucasian hypothesis links Sino-Tibetan to languages of Siberia and the Caucasus. On the basis of lexicostatistics, Sergei Starostin additionally hypothesized an even larger Dené–Daic macrofamily which incorporates both Dené–Caucasian and Austric as primary branches.
Genetic similarities between the peoples of East and Southeast Asia have led some scholars such as George van Driem to speculate about "Haplogroup O languages".
