I have mentioned in previous posts about places to go see when doing your visa run.
If you take the road back towards Prasat, Surin about 20km north of Kap Chueng is a left turning which is sign posted for Ban Kruat and Amphoe Dong Rak. Take the left turn, you are heading for Amphoe Dong rak, where Prasat Ta Muen, Prasat Ta Muan Toc, Prasat Ta Muan Thom are located. These are ruins from the ancient Khmer empire, which are situated rite on the Cambodian border.They are sign posted, but make sure that you take the second turning after the sign post. Its confusing I know, but this is the right way. In the past it was recommended that you informed the Border Police if visiting here, as it’s as close as you get to Cambodia with out crossing the border. The Khmer Rouge used it as a place of entry to cross over into Thailand and it was one of the heaviest land mined areas in the world. The atmosphere is electric, giving you a real sense of the recent history. It’s perfectly safe, just remember keep to the paths and don’t stick your hands into places where they should not go, due to the large snake population.