It looks like we might be looking for similar itineraries (I'm also using SPG points) http://www.flyertalk.com/forum/thail...rst-timer.html

Keep in mind I have not been.. so the below is based on reading FT and other sources.

When are you going and how much are you looking to spend?

The better SPG hotels in Ko Samui (W, Vanna Belle) are very expensive on points. You can stay at the Le Meridien for something reasonable but it doesn't have much of a beach and the villas don't have much view or natural light.

In Phuket, the Westin Siray Bay looks nice but does not have a great beach. The LM Phuket is massive and just didnt look that appealing.

I read that the area around Krabi is nice and it is probably a very good option, but the pictures of the Sheraton didn't really give that "wow" factor that some of the other Thai resorts did.

I would suggest doing a few days each in Bangkok and Chiang Mai, then based on how much you want to spend, either doing several days in Ko Samui or heading down to Krabi. A combo of Krabi and the Westin Siray Bay is also possible. The advantage of this is that you can generally fly out internationally from Phuket airport (HKT) which is much more convenient then Ko Samui or Krabi airport.

If you want more time in Bangkok and Chiang Mai, another option would be the Sheraton Pattaya, which is driving distance from Bangkok.