I was wondering, since a few Asian languages sound alike to Chinese words. When I listen to Thai, it sounds very similar to Cantonese. And I pick up several words in Filipino, Japanese and Korean that sounds the same when spoken in Chinese. I guess this would be similar to Latin developing into French, Spanish, Italian etc.
No. Not at all. South Asia generally refers to the subcontinent which includes the countries of Pakistan, India, Bangladesh, and Sri Lanka. The two language families spoken in this area are indo-european in the north and dravidian in the south. The Chinese languages are mostly members of the sino-tibetan language family.
Sinolinguistics is pretty complicated, you might try asking in /r/linguistics!