Did a search here on FT and didn't see anyone post about it before. I just read that a Park Hyatt will be opening at Koh Samui. It sounds really nice:

http://www.hotelexecutive.com/newswire/pub/_26268.asp

However, this doesn't seem to be on Hyatt's list of future hotels, so maybe it won't materialize, like past plans for a Park Hyatt in Dublin and Macau.

Hyatt seems to be doing a big push in Thailand with other upcoming hotels in Chiang Mai, Phuket and the recently opened Hua Hin.