We have stayed during a week at The Kala Samui. It has been a lovely experience. This hotel combines the rustic island spirit (wood-made facilities, coconuts everywhere either in decoration either to indicate "don't disturb" & "clean up room" signs!, lot of nature inside the hotel and at surroundings) with modern comforts (infinity pool, international assorted breakfast until 6 pm !!!, very nice pool bar service, air conditioning, free wifi, free kayaking & snorkeling activities, etc).
The hotel is placed within a little cliff which provides a charming ambiance to a beautiful spot, with a lovely view to the sea, rocks & beach (not far away from the hotel).
Very close to lamai (10 minutes by car/motorbike).
Nice restaurant with many choices (international & thai), however a little expensive compared to other restaurants in the same area.
Very nice staff, sometimes with some problems in english communication but good enough.
Wifi a little slow.
The only negative point was about the air conditioning in the room. The temperature-isolation of the room was not so good, so, once the air-conditioning was off, the fresh air was not kept inside and it was rapidly replaced with the hot air from the outside. It forced us to keep the air conditioning on during the whole night or wake up to periodically turn it on for while and turn it off later.
Beside this issue, amazing hotel, which I recommends!