Song Saa

Located on the Gulf of Thailand, the island boasts crystal clear waters and is a 30-minute speedboat ride from the coastal town of Sihanoukville. 
All of their 27 villas are built from sustainable materials, come with its own private pool, WiFi and are modeled after Cambodian fishing villages (expect thatch roofs, rough-hewn natural timbers and drift wood furnishings). The Jungle villa serves up views of the surrounding tropical rainforests while the Oceanwater villa gives you direct access to the ocean from your balcony. What’s more, the resort functions on an “Always Incuded Rates”, which mean that you pay a flat rate for the villa each night and it includes all meals (yes, even breakfast in bed or a romantic dinner on the beach), drinks such as house wines, spirits, beers and non alcoholic drinks, speed boat transfers, free use of kayaks, sailing boats and snorkeling gear and guided tours of Song Saa’s marine reserves. 
Unlike your typical spas, the Song Saa Sanctuaries has treatment rooms scattered across the island. Think outdoor salas, discreet treatment villas encircled by thick rainforests and a couple peppered along the shore. It offers Khmer treatments using local herbs, sand and iron-rich stones. 
Villa rates start from US$1,117 ($1,528) per night. Head here for more info.