Koh Rong
Koh Rong is only tourist amenities which were handful bungalows besides miles of dense jungle and gorgeous white sand beaches. It is still possible to find solitude on some of the more remote parts of the island. Recently, dozens of cheap accommodations have been built and the place has become a backpacker Shangri-La.
Koh Rong Samloem
If you want something even more secluded and quiet, be sure to head to Koh Rong Samloem before your journey ends in Cambodia. The area is more local, there are fewer tourists, so do not miss the fresh and clear beaches here.
One of the most noteworthy things to do on the island is to swim with plankton. Kayaking is a must-do attraction on the island of Koh Rong Samloem, where the waters are graced with sporadic land masses, making it an intriguing place to explore on water.
Koh Tang
The waters around the uninhabited Koh Tang island are known as the site of the infamous Mayagüez incident of 1975 in which the Khmer Rouge captured a US ship. They also offer world-class diving, unspoilt by crowds. Five hours from the mainland and best visited as part of a live-aboard trip, divers are rewarded with a stunning diversity of corals and rocky reef dives where you're likely to see barracudas, octopus and seahorses. If you do not fancy a live-aboard, head to Koh Rong Saloem, much closer to Sihanoukville. Here you will dive with kingfish, moray eels and a wide variety of nudibranch. The island is pretty enough to warrant a few nights of post-dive chilling.
Koh Thmei
Located inside Ream National Park, Koh Thmei is home to monkeys, civets, lizards, more than 100 different species of birds and several threatened species, including the fishing cat, a wetland feline than makes its home near streams and mangrove forests.
The island has only one place to stay, Koh Thmei Resort, and the term "resort" is used loosely. It is little more than seven simple wooden bungalows, but it is eco-friendly and solar powered. Tourists can hike, bird-watch, snorkel or take the two-person sea kayak out for a spin. There are nearby deserted beaches to visit with occasional views of dolphins swimming along the coast.
Koh Tonsay
Only 20 minutes by boat from Kep, Koh Tonsay was Cambodia's premier resort in the 1920s, and is now inhabited by only half-a-dozen Khmer families who run the beach-side huts and restaurants. The two palm-fringed beaches both have shallow waters perfect for snorkelling and there is nothing more demanding to do all day but swing in your hammock with a cold beer. Generator electricity is available only between 6pm and 9pm, but that is all the better for listening to the night cicadas and gazing at the starry skies.