It's pretty isolated, actually, and proud of it -- the whole southern end of the island prides itself on being the least built up area, which is not everyone's cup of tea. Laem Set Inn is probably about 10 minutes (by motor) from Lamai. You could walk it, too, but it would take a while. When I was there, my wife and I drank on the beach from our minibar.

Lamai itself might be more your style if you'd like to walk to bars, or Bo Phut (a very charming little town) if you don't mind only being able to walk to a few bars.

The only place in Samui, in my experience, where you really feel like you're in the thick of an entertainment district is Chaweng, which is very densely populated with nightspots. But Chaweng borders on sleazy for me--quite a lot of sex tourism and loads of sunburned drunks. I have nothing against sunburned drunks, of course, I just like fewer of them when I go to the beach.

i would recommend booking a place in advance (now that all the resorts seem to have websites) if you are coming in within five days before the full moon -- if you're a hard-core young partier, stay in haad rin, but otherwise, stay over the hill in baan kai or baan tai. a year or so ago i stayed at the dewshore bungalows, because they had one remaining old-school funky bungalow right on the beach, which is what i like, and also a big fancy new pool (all the places are putting pools in) which is a great thing to have in the hot afternoons. there are some chill places on the northwest end too, but that's a trek to get to the full moon by taxi.

the sanctuary is pricey, and only accessible by boat. if you're into healing and cleansing and don't care about the money, give it a shot, but it means that your only transportation to and from the full moon party is by boat, which to me (having lived there for a while) is less than desirable for a return trip -- easy to miss your boat, and if the waves are high then it might leave from the other side. to me, a truck taxi is easier, since they run all night (if there are enough passengers to go). there are cheaper places near the sanctuary as well.

depending on your timing, it might be work staying in haad rin a few days for the party, then heading up to somewhere quieter, like tong nai pan or than sadet -- really, anywhere gets quieter after the party ;^)

and i'm not sure why you'll be in bkk for a week, but as someone who travels there often, that is waaaaay too long unless you absolutely have to be. last month, i was there five days and vowed i'll never stay more than 3 days again.

Leslie just said pretty much everything I was going to. Good advice. The good news is there's lots of options, the only trouble comes when you try to show up just before the party.