Guandao
Rajah of Minyue and Langkasuka
The Srivijaya occupied the Mekong Delta, and when the locals revolted, they became the Khmer. Perhaps offshoot is not the correct term, but that's how the Khmer connect to Indonesia.
Didn't even realize the Srivijaya's reach expanded that far. I think the whole of medieval Southeast Asian history will be reflected in the scenario (Mongol invasions, Indian influence/trade, Chinese trade, battles between the SE Asian nations). Hopefully, it'll be fun.