We have about 12 days early december, just can't decide whether to spend them all in 1 place, or to combine khao lak and ko lanta. We did the gulf of thailand last year, three islands in 12 days which suited us perfectly. We like to take some dives, Khao Lak would be our preference for that. Khao Sok National Park is close and looks like an interesting day trip, so Khao Lak look like a good base to me. But maybe after 5 or 6 nights it would be time to go someplace else, I know I get restless if I stay in the same hotel too long. Ko Lanta is also on my list. We fly in and out of Bangkok, haven't booked any domestic flights yet, trying to put the itinerary together, maybe you can help ?