Koh Lanta is a group of islands on the west coast of Southern Thailand.
It has a very laid back, kind of hippie-ish vibe. Getting around by hitchhiking is very easy. Most locals drive pick ups and will let you jump in the back for a few kilometres. English is widely understood.
Note that on all of the ferries to, from and between the islands, one has to pay for each passenger in a vehicle. It's are only between 7 and 11 Baht though.