Where to Stay
You should really stay in Haad Rin, which is where the full moon party takes place.A lot of people make the mistake of staying elsewhere on the island, so be smart and book a place in advance or else you will be taking 20 minute cabs every day and night. I would recommend Neptune’s Villa and Cocohut (have great pools), but there are tons of cheaper hostels as well. There are even places on the actual full moon beach you can sleep. There are no hostels in particular that really stand out so do a little research to see what is best for you (as long as you are in Haad Rin). Be aware that most hostels/hotels will make you stay for 5 nights minimum. This is very standard and if you don’t have the time then you will have to eat the cost of those extra days.
Where to Party
Make sure you are in town for a full moon party and if that is not possible a half moon. The former is on the beach and the latter is in the jungle. The days leading up to these MASSIVE parties are also amazing. You will hear through signs and word of mouth what is going on each night on the island. Try to hit a pool party, a jungle party and spend at least a night or two on the main full moon beach (Cactus is usually bumping). Really, just walk around town and walk into any bar/party- you can’t go wrong. Everyone drinks buckets (large drinks with hard alcohol, red bull and soda) from vendors but if you want to save money buy liquor at a store during the day and make your own. If you don’t see the sunrise every night, something is wrong. You will also see a lot of cool fire activities at night including jump robe, twirling, slides, etc.
The music here is amazing and there is really something for everyone. You will hear a lot of psy-trance and of course, a lot of Top 40. Keep your ear out for great techno/deep house as well, especially at the jungle parties and at the full moon party. The Full Moon Party has several different stages, each playing different genres of music, so be sure to check them out (they even have a dubstep stage).
During the Day
Most people relax during the day and hang by the pools; however, you can go on cool hikes or even scuba dive if you want. You can also watch or learn Muay Thai.