Domestic flights in thailand?

Buying an air ticket online is pretty much the same price if you go to a travel agent. If you have a fixed date you want to travel to the island and are travelling in peak season, book online. If you want to take your trip as it comes, with no fixed plans and are not travelling during peak season, then you will be safe to book your flights from a travel agent. If booking from a travel agent, check the internet first to compare prices. Flights may be cheaper if you book in advance and take the 'early bird' flights.