Koh Yao Yai sits in the middle of Phang Nga Bay, and the view from this resort is the one people come to Thailand for: limestone karsts rising straight out of the water, with almost nothing built between you and them. Villas run along the sand and up the low hillside behind it.
The island itself is largely Muslim fishing and rubber-farming communities, quiet and easy to explore by bicycle. Speedboat transfers connect to both Phuket and Krabi, so it drops neatly into an itinerary from either side.