I've been living and traveling around Asia (mostly southeast) for the past two years. The budget airilnes are hit or miss with prices but generally are cheaper than airlines like Malaysia or Singapore. I've never tried the backpacking circuit route, though. Have you looked at FlyScoot, Jetstar, or Tiger? Also it depends on when you travel - if it's early next year, it'll coincide with Chinese New Year when prices become ludicrously expensive to countries like Malaysia, HK, Taiwan, etc. Hope that helps