Was in Thailand a few months ago, but i went to Malaysia, Singapore and Indonesia instead.
Go to full moon party as said, but apart from that just buy a lonely planet book, plus you will meet loads of people who will tell you all the good places to go
Best advice yet, let the lonely planet book be YOUR BIBLE! you'll get people pulling you off to "guesthouses" and hostels etc etc as soon as they see a white face with a backpack. but if its not in the book just dont do it. its that simple. 3rd world country, different language, your going to get into trouble very easy.
having said that i'm not trying to dampen it, its an amazing place, try ko-chang its an island off the south, 4 hours on coach from bangkok. mint.
*edit* and i forgot the rules
dont drink the water, dont eat the veg and always check for a penis
