If you think you've heard of this small island 10km north of Koh Samui, that's because its Full Moon Parties are world-famous. Once a month in the southerly village of Haad Rin, 5,000 to 10,000 people gather to watch the yellow moon rise over the horizon, and then lose themselves in dance, drink and drugs. Maybe it's just us, but it seems to draw an ever younger crowd of year-offers and twenty-somethings. If you arrive on full moon day itself, chances are you won't find any room at the inn, but you could check out one of the quieter, spin-off Full Moon Parties on nearby beaches. And, while we're in middle-aged mood, do remember that drugs are illegal in Thailand.
The island's capital is Thong Sala on the west side, where most of the boats dock, including the Samui - Koh Pha Ngan - Koh Tao ferries. But there's not much to hold you there, so jump on one of the waiting songthaews and head to a secluded beach - our favourites are Chaloklum in the north, a traditional jungle-backed fishing village with little to do other than sunbathe and swim; Mae Haad in the northwest, where the sea is as flat as a sheet and ideal for snorkelling; and sheltered Than Sadet in the northeast, which is backed by jungle waterfalls.