737 vs A320
The A320 rating will give you access to every airline operating the 318/319/320/321. If you go the boeing route, you will still have to choose between NG and classic, as there is still a fair amount of those flying in SE Asia.
The points made in other threads about your low hours to age ratio and the 500 hours on type have some validity, however I can assure you first hand there are airlines recruiting type rated people with similar profile to yours with no hours on type.
Your plan could be a solution to a quick career fix, the region is booming, and you could be in command of a new shiny jet within no time.
At the end of the day, it is down to you having the confidence to invest in a type rating. I know I did it a few years back and it paid of.