I am currently in Bangkok after returning from my first trip to Siem Reap to see the Angkor Wat.
I had a learning experience when crossing over to Cambodia at Piopet. My friend and i were approached by several 'touts' re onward travel to Siem Reap. A 300B bus sounded good. However beware!!!!! We had to wait around for an hour or so until they got more passengers. Do not expect a luxury bus and the road is unsealed and pretty awful. I don't recommend it if you have a bad back!! The bus broke down and we were taken straight to a guesthouse on our late arrival at Siem Reap. It was nice enough but after speaking to others who had done the route this form of 'hijacking' seems common place.