AK - spent a few weeks in Thailand and Malaysia and more than a month in Indonesia. Would definetly recommend all of them. Very cheap, nice people and quite an experience.
Thailand is a blast, don't spend too much time in Bankok, a couple days and you should be all set. See some Thai boxing at lumpeenee stadium, visit the grand palace and hit up Pat Phong road (the "shows" Thailand is famous for). Would really recommend the islands in the Gulf of Thailand too...scuba diving is top notch there. Spent less time in Malaysia as there were riots in Kuala Lumpur at the time...but aboslutely loved Indonesia. Great surfing, scuba diving (Gili Islands) and partying. We actually partied in the Sari Club that was blown up in Bali many nights. Not surprised they chose that one to hit as it was one of the only clubs that would not allow locals from Indo into the bar. A tragedy on many levels. Have a blast and be carefull....