Do I really need to buy a checked bag?

Yes, if you aren't packing extremely light. Many Asian budget airlines strictly enforce a 7kg carry-on limit and will weigh your backpack at the boarding gate.

Is it cheaper to book one-way or round-trip?

In Asia, it is almost always cheaper and more flexible to book two one-way tickets on different budget airlines.

How to Book Budget Flights in Asia

Use a combination of regional budget airline websites and flight aggregators like Google Flights to compare routes. Book at least 21 days in advance and be prepared to pay extra for luggage, as budget carriers in Asia strictly enforce weight limits.

Use the right search engines. Start with Google Flights or Skyscanner to see all carriers on a route. However, always double-check the airline's direct website before booking, as regional carriers like AirAsia, VietJet, or Cebu Pacific sometimes offer exclusive 'member' fares not found on third-party sites.
Check secondary airports. Asia is full of secondary airports that budget airlines prefer because they have lower landing fees. For example, use Don Mueang (DMK) instead of Suvarnabhumi (BKK) in Bangkok, or Clark (CRK) instead of Manila (MNL) in the Philippines.
Factor in 'hidden' fees. Budget airlines in Asia make their money on add-ons. Assume your ticket does not include checked bags, seat selection, or meals. Pre-book your luggage weight online during the booking process; paying for extra weight at the airport gate can cost 3x more.
Leverage regional currency. If you are booking directly on an airline's site, check if the price is cheaper when you pay in the local currency of the airline’s home country. Use a credit card with no foreign transaction fees to avoid losing money on the conversion.

Do I really need to buy a checked bag?: Yes, if you aren't packing extremely light. Many Asian budget airlines strictly enforce a 7kg carry-on limit and will weigh your backpack at the boarding gate.
Is it cheaper to book one-way or round-trip?: In Asia, it is almost always cheaper and more flexible to book two one-way tickets on different budget airlines.