Ko Pha Ngan, next in size and popularity, just to the north of Ko Samui, is home to the infamous full moon parties -- massive drug and alcohol fuelled all-night parties -- often attracting five to ten thousand people. Centred around what was once the most stunning beach on the island, Haad Rin, the beach now a Jekyll and Hyde affair, alternating between being a still rather pretty, though over-developed white sand beach; and a festering filthy armpit filled with ravers, drunken yobs, undercover police and some pretty slippery characters -- all depending on the phase of the moon -- we tend to steer clear of Haad Rin during the party! Parts of the rest of Ko Pha Ngan, particularly on the west and east coasts are still very good value -- pick and choose and you'll have a great time.