Jarvis addresses some interesting points. For sure Yamaha want to go to Indonesia. When I was there 3 years ago, I couldn't believe my eyes when I watched a race on TV: the whole studio was in Yamaha decals, and the hosts were dressed in (official!) Yamah team colors. Advertisement nearly everywhere.. Well, Yamaha is big there, but the point is that MotoGP is big there, too, on a huge societal level. Lorenzo and Rossi smiling from ads every few hundred meters. Simply for that they would deserve to have a GP! [And it answers povol's last remark, regarding potential attendance]
As far as the rest of SE-Asia is concerned - I think MotoGP (and other major motorsports, F1 etc.) should have gone to Thailand a long time ago. They are really well developed, are quite much into technology, and racing is big there. Not so sure about Vietnam (though I have never seen so many motorbikes - though mostly scooters - in one place than in Hanoi!). India is a must, anyway. And China, too - I cannot understand why MotoGP moved away from there. Almost every business is expanding to China. Like it or not (I don't), but there's hardly a way around it.
What stuns me most is that MotoGP already has been in some of those places. Same with South America. So there are even a handful of places with experience of hosting a MotoGP round, and some others that did 'at least' F1.