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.
Hyatt did have a property in Macau as recently as 3 years ago, in fact it hosted one of my favourite restaurants which also seemd to disappear along with the Hyatt name.