We were only in Siem Reap for 3-nights but ended up liking Khmer Kitchen so much that we ate there twice. It’s tucked away in a nameless alley behind the market but every tuk-tuk driver knows it so it shouldn’t be hard to find. Not only was the food really good, I think our total bill was something like $6USD for the two of us.
The place has a huge menu but our favorite dish was Fish A-Mok. A-Mok is a rather mild curry that can be ordered with shrimp, pork, chicken, beef or vegetables. We found the recipe on the web site of a place we ate at in Phnom Phen and have been making it at home since we got back.
We're in the process of planning another trip to Siem Reap and expect to eat at Khmer Kitchen on the first night we're there.