With your Starwood Platinum status you might really like Le Meridien Khao Lak, a beautiful property on an extremely long beach that has some nice, inexpensive eateries and open air massage shacks on it and that is not overbuilt (i.e., still has lots of empty stretches). With your status, I'd think that you'd at least get an upgrade, quite possibly to a suite or maybe even a beach villa...or for a modest price you could pay for a villa upgrade. It's about a 75 minute drive from Phuket airport, so if you wished you'd be able to skip Bangkok and fly in directly from Hong Kong or Singapore.

One big caveat, though, re you October plans. Since it's the rainy season in much of SE Asia, some of those great beach eateries in Khao Lak might be closed and more generally you'd want to check what the climate is like that time of year in any place you'd be considering.