There are a lot of private operators offering Siem Reap–Bangkok tickets virtually at every corner in Siem Reap. Sometimes tickets from Siem Reap to Bangkok or Pattaya are sold at as low as USD15. While travelling with these operators you will definitely reach your destination, be aware, though, that your journey may last much longer than expected due to that usual Cambodian perception of ‘good service’. What you will have is likely to be a worn out bus with extremely limited luggage space – actually backpacks and suitcases are piled right in the aisle. Even if nowadays the road between Siem Reap and Poipet boasts quite a decent roadway covering, these buses tend to spend from four to five hours instead of two to reach the border as they call in at a number of souvenir shops and cafes on their way in a hope to wheedle some dollars out of your pockets. No use in arguing, just take it for granted that your journey will be a long one.