It was only to be expected that as Samui itself became more mainstream, the backpacker set would look for newer places off the beaten track (read: cheap). As it turns out, they didn't have to look far. A short ferry ride north from Samui brings you to Koh Phangan.
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Even smaller than Samui, most of Pangan is still in pristine condition and the best way to get around the island, from one beach to another, is by boat. This is not to say the island is completely unspoiled. On the night of each full moon, the main beach plays host to the "full moon party", a night of complete, drug and alcohol induced debauchery, if you believe the press.