We found a nano SIM for my wife's unlocked iPhone 5S last year. Actually, it was the regular sized SIM but most of the shops all have SIM cutters. No problem. I believe I paid about 200,000d for the SIM, which came with quite a bundle of minutes and data as well. I think I paid too much but it was for the wife's phone :-)
The SIM for my unlocked Galaxy S2 was standard size, and I bought it with some minutes for 50,000d (no data). I cannot speak for what you many encounter elsewhere in SEA. Good luck and Happy travels!