Both RC Reserves (Krabi and Mandapa) are great but they have impressive price tags too.

St Regis Bali is another contender, although being a much larger resort, they wont be able to offer personalised service like the Reserves.

If you willing to go to more remote location, Ta'aktana Resort (Luxury Collection) Labuan Bajo is another great property.
Accessibility still an issue there as they only have direct flight from Jakarta or Denpasar.