Here is a report on a recent trip to Siem Reap. Often touted as a genuine gay alternative to Pattaya I have to say that in my opinion is is certainly not. While a nice town and with plenty to do and enjoy the gay action is very limited.
For a start there isn't a genuine gay bar. Linga Bar has closed and neither Miss Wong's or Station bar are particularly interesting and both were pretty much empty every time I went past.
Massage places are the only real way to find some action. Hertha Khmer and Blue Hertha are owned by the same person, both have a selection of about ten masseurs but they were not especially attractive to my eyes. Also their facilities are poor to say the least so often the masseur and yourself will go unshowered. They all quote $40 dollars for an hour of 'special massage' but will all come down to $30. So with the fee paid to the host establishment you're looking at prices similar to Pattaya but with no where near the quality. IMO.
There is a road close to Pub Street that has about 5/6 massage places. These are basically for non-sexual body massages carried out in a chair at the front but most have some boys working there and all offer 'special massage' upstairs. But the boys come and go so you might need to walk up and down a few times before you see someone you like or a boy you noticed before.
I also visited MENs resort and spa. It's very nice and I went there for a massage but none of the staff seemed very interested so I didn't bother. It struck me as rather steeply priced to stay there compared to my hotel which was cheaper and considerably more luxurious. Also be aware that it is located down a rather potholed alley so at night walking might be difficult for some and I had to get out of the tuktuk and walk such was the discomfort of the ride.
So, to sum up. I found Siem Reap a lovely town to visit but I wouldn't go again and it is definitely not an alternative to Pattaya.