Minimee...

There are no international border crossings that I am aware of linking Buriram to Cambodia. The nearest crossing is Chong Chom / Osmach Border in Surin Province. I'm guessing the driving time from Buriram via Chong Chom to Siem Reap would be 6-7 hours - which is about the same amount of time I figured it would take me a few years back traveling from my home/village in Si Saket Province which was right on the Thai/Cambodian border.

Andrew, be aware of the border scams - they change with the wind.