Koh Samui has had its own airport since 1988 and it is privately owned by Bangkok Airways. Many worldwide operators offer packages including international flights to Bangkok and Surat Thani, with the rest of the trip being made by bus and boat in order to avoid paying the heavy Koh Samui airport taxes imposed by Bangkok Airways.
Other flights arrive at Surat Thani airport from where you will be transferred by bus to Donsak (about 70 km ) in order to catch the boat to Koh Samui. With Air Asia, the boat will take place with the “Raja Ferry” company and you will therefore arrive at Lipa Noi’s harbour. With Nok Air, the transfer will be organized with the Lomprayah company and will therefor arrive at Nathon port.
For return tickets with both of these companies expect to pay around 4,000 baht.
The other two airlines flying to Surat Thani from Bangkok are Thai Air Smile and Thai Lion Air, please note that these two last companies do not provide you with a transfer to Koh Samui. Therefore you will have to buy your ticket to reach Samui on your own.
Timing : For your transfer from Surat Thani airport to Koh Samui, plan on spending around 3 and a half to 4 hours in total for the trip, (2 hours on the minibus and 1 and a half hours on the boat.)
Travelling like this will save you around 30 % compared to a direct plane ticket from Bangkok-Koh Samui.
Remember to take into account that the last boat to Samui leaves Donsak’ s port at 7 pm.