ko samui -overbuilt-chaweng best beach
ko phangan-better and less expensive but no really good beach.
ko tao great deals on scuba training and great scuba sites.
Phuket-sex, drugs, shopping and rock and roll. some nice secluded beaches out of town, north from there is kow Lak great beach better vibes.
ko phi phi. nice boat trip from phuket, they filmed the beach w/dicaprio there.
Ko lanta my perfect beach, family oriented
peaceful no hassles and very clean.
be sure to go to chiang mai and do a trek up north nice folks.