Some pretty different cultures would arise. Depends on where Malays go, and what happens to there neighbors. Assuming a similar culture arises in India and China, southeast Asia would probably be highly influenced by them. So many butterflies though. It would be interesting to see a TL on this, or similar population developments take different courses than OTL, especially this far back. Lands of Red and Gold kinda show this with just Australian Aborigines having developed an agricultural and urban society.