A cheaper alternative is to fly to Surat Thani, and from there to go to Koh Samui. Surat Thani Airport is around one hour away from Donsak, the place where most of the ferries to Koh Samui leave. From Donsak, it is a nice boat trip from approx. 1,5 hours to Nathong, the "capital" of Koh Samui.
