My girlfriend and I (both 25) stayed here for 1 night during our week long stay in Sihaunoukville. We only paid $13 for one night which was as cheaper than anything we could find. I spent the full day in the room ill and it wasn't a bad place to recover. The air con worked well, the TV had some decent movie channels and there was hot water all the time.
The room itself was a good size with a wardrobe and a TV. No fridge or safe and the WiFi only worked at reception which wasn't ideal but its so cheap. The only reason we moved is because my girlfriend wanted a pool to relax by while I recovered from my stomach bug. Otherwise we'd have stayed for 3 or 4 more nights no problem.
The location was ideal, 5 minute walk to either ocheteaul or serependipity beach and all the bars and restaurants.
The only bad thing I'd say was the double bed was quite small, and we are both quite slim. Also the 2 windows had no curtains so the room was bright from 6am.
Overall I'd fully recommend Koh pos of you're on a budgert like us as it's just as good as another place we stayed paying $22 per night.