Why? The largest of the southeastern Thailand's three islands, Koh Samui is the most accessible from the mainland. Chaweng Beach has the best hostels, guesthouses, bars and clubs, further along the coast either side are some unreal spas and night spots, and the nearby Ang Thong National Marine Park will give Koh Phi Phi a run for its money.
Why? This tiny island north of Koh Phangan translates to 'Turtle Island'. Figure it out for yourself. With the clearest waters and the best diving schools, Tao is the go-to destination for your PADI Open Water certification. Back on land, there's a handful of amazing beaches (what? In Thailand? Really?), complete with cool bars and hostels nestled under swaying palms.