I stayed here with my family in December 2011, and have stayed multiple times on my own or with friends since 1996.
The best thing about this place is that it is right next door to Khao Sok National Park. The property was established in the early 90s with nature tourism in mind. The family that owns the resort have managed to keep some nice forest remaining. You can hear gibbons calling, and see macaques and hornbills fly across the property in the mornings. The water in the stream is very clean and you can usually see small fishes poking about between the rocks since there are no other developments upstream.
The property has gone through much development in that time with the number of bungalows expanding from 5 to more than 20. The best rooms to stay in are the new treehouses. They are well-designed, comfortable rooms with balconies and clean bathrooms in the rear of the property on a hill with views eastwards over the beautiful karst mountains. Small children may find the steps up to the treehouses a bit steep. The next best rooms are the new riverhouses in the east of the property which have aircon and nice balconies, and again clean bathrooms. The older concrete bungalows near the restaurant are a bit small and cramped inside. The original bungalows on the hill overlooking the khlong (river) were built from timber and are now in need of repair.
This is a family operation and they are lovely people from Surat Thani Province. Khun O is the young lady who manages the property for her father Khun Anothai. I have found they try their best to please guests once you tell them your needs. If you need your room cleaned make sure you tell them in the morning.
The food is really excellent with a range of original Thai dishes. There are two levels to the restaurant which can get crowded when there are groups coming through and staying during the high season. Be patient with the cooks who will turn out a nice meal for you. Banana and pineapple pancakes are a breakfast specialty, definitely worth trying. Try any of the curries or local fish dishes.
It is worth taking a trip to the Chiew Larn Lake inside Khao Sok National Park. This is best done as a day-trip because the Rainforest Resort is much nicer place to sleep than the rowdy floating rafts on the lake. If you are into nature watching, you don't even need to walk into the park. At the restaurant you can watch a range of small birds feeding in the flowering trees and bushes, or just watch them from the balcony of your bungalow with a nice cup of coffee in the morning, or a beer in the late afternoon. At night you can spot frogs in the river and ponds around the property. You might pick up a few leeches in the process but that is par for the course and they come off with a squirt of insect repellant. Avoid going to the Monkey Temple since the macaques there are fed garbage by tourists and it disturbs their natural movement and behaviour.
The best time to visit Khao Sok is October - December at the end of the low season when the temperatures are relatively cool (up to 30 Celsius) and there are fewer visitors. But I have been there in August and September when it's raining heavily and the place is beautiful and very quiet there.
There is an internet service if you really have to connect but it's not always reliable. The digital GSM telephone signal is good.
Because I would not recommend the cheaper bungalows, this place is not the best choice for backpackers. It's really best considered a mid-range resort and it's good value relative to what else is available in the area in that category. You can make bookings online. They have a website at http://krabidir.com/khaosokrainforest/