South-East Asia is so different, both culturally and politically, that a war between any of the nations is possible. For ATL wars, Indonesia-Malaysia, Vietnam-Cambodia, Thailand-all its neighbors.
OTL, since 1980 I think a few skirmishes between Thailand and Cambodia occurred just last year, and the East Timorese situation happened back in the late 90's. Peaceful revolutions that could otherwise turn into a deadly violent civil war happened in both Thailand and Indonesia. A failed attempt at this also occurred in Myanmar. Oh and Acehnese rebels were fighting against Indonesian government troops until 2004, when they signed a treaty. The Papuan independence movement is sort of a joke and can be compared to the Basque 'revolutionaries' - they're no more than terrorists.
So yes, there have been a few acts of violence in SE Asia since 1980 but nothing that can actually be considered 'war' IMO.