Gone are the days where you would fly national carriers between countries. If you talked to someone in your dad’s generation, they probably would tell you it costs thousands of dollars to fly around on vacation. That was yesterday’s method of travel.
These days, you would fly a national carrier to the continent that you want to reach, then fly a local low cost carrier between the countries there.
South East Asia is one area where there are many competitive low cost carriers (LCC) is in South East Asia. There are many many options in the region, with Malaysia, Indonesia, Singapore and Thailand offering a LCC.
A great way to figure out prices is to use an aggregate service such as SkyScanner to determine the general prices during the time frame you want to travel, then head to individual web sites to get the actual prices.
Among them, I find AirAsia to be the best. The service is great and in my experience, often on time. Furthermore, aside from standard safety regulations prohibiting particular items, they are quite flexible with the number of items you bring on board.