On our visit to Angkor Wat, our tour guide told us that by climbing the the higher levels we would reach Heaven. Turns out that was Pebble Resort in Koh Ron Samloem.
The resort is gorgeous, with a beautiful beach, clear and mostly warm water (obviously weather helps!) and the bungalow we had was stunning, set as if in the jungle of the island. The cocktails were fantastic (though we twice drank them out of mint for mojitos!) and the food was excellent. The vibe is very chilled, and you are very clearly away from the more bustling side of the island. Beware that the ferry across doesn't offer it on their website, but it is generally the stop after Saracen Bay, and they need to know to stop there!
We only stayed for one night, but it was enough to seal this place in our top 3 hotels we've ever stayed at.