Combined flight + minivan tickets
Low-cost airlines Air Asia and Nok Air offer combined flight + minivan (and sometimes ferry) tickets to the most popular islands and to some destinations without an airport. They are a good option to get to Koh Samui and the neighboring islands, as direct flights from Bangkok, Chiang Mai, Krabi or Phuket are very expensive due to Bangkok Airways' monopoly.
They also go to places such as Surin, Phang Nga, Khao Sok and Ao Nang (Krabi), and you are looked after from start to finish, which makes connections easier.