Cambodian beer gardens are a very particular and very specific insitution. I should do a real article on them. They're tantamount to European beer gardens in that they revolve around late night alcohol consumption, shooting the shit with friends, and overeating. Except in Cambodia, beer gardens also usually feature a giant roasted calf, a few dishes involving eel/insects (for when you're really punchy) and in the better kind of places, either karaoeke or a confused looking real live singer. Beer gardens are always ferociously rocking with Khmer party-people on the weekends (and most nights, really) and they are good places to eat as well. Gotta wash down the beer with something.
I go to Prom Bayon because it is near my place of employment, inexpensive, and the food is pretty good. I've had lunch here, I've had dinner here. Dinner is when the place comes to life, with packs of heavy drinking and rowdy Khmer's filling the place up, but it isn't half bad for lunch, either.
I get their loc-lac a lot. They have Khmer style, which doesn't comes with french-fries and a more peppery and less ketchupy sauce. They also do it American/English style, which means more ketchup and more french-fries, the tenets of the Western diet. They have tasty stir-fried eel. Good Khmer style raw-beef salads with a ton of herbs and lemongrass. Excellent grilled, rare beef with pepper sauce, which is one of my all time favorite accompaniments to alcohol.
Beware the salad section. I thought I was ordering the tasty herb beef salad one day and got the salad which was "boiled beef organs with an assortment of greens on ice." I ate it - tripe is tripe - but it wasn't really what I was after, if you get the drift.
Service is in the finest beer-garden tradition of "extremely surly." I would expect nothing less. There is usually an offensive or incredibly violent movie playing on the television set indoors during lunchtime, which I consider a real added-value. Your mileage may vary, but you also live in Cambodia, so I can guess at your tastes. I sure can.