Thanks all for the comments, they're very, very much appreciated. I'm glad I checked here because I was very close to booking something on Samui. I'll be taking a look at the Aman properties in Nha Trang and Bali instead.
I am keen to minimize travel time -- we're adventurous people who want a breadth of experiences, so we're already cramming in a lot: Kuala Lumpur, Ipoh, Cameron Highlands, and [NICE BEACH RESORT HERE]. However, both those suggestions have direct flights from KUL and are only 1-2 hours extra which I suppose is tolerable.