Was wondering where you can get a bike from and how much they charge?
Sorry we did it with a Tuk Tuk for the day 18 USD.
But yes next time we will do the bicycle option although it gets hot very quickly.
We got them through Travel China Guide as part of our tour package (guide, lunch and transportation). It is not only about renting the bike, but also knowing where to go (off road on the wall of the city), and getting the presentation of the monuments at each and every stop.
The rental company brought the bikes at the starting point and was waiting for us at each visit site to watch over the bike.
I am sure the hotel where you plan to stay can also give you some name of company directly in Siem Reap.
Sorry this is probably not the answer you were looking for...
Get quick answers from Angkor Thom staff and past visitors.