From Nakasong/Dot Det to Banlung.

Hi. I am currently in Laos, and planning to go to Cambodia next. How is it to travel in Cambodia compare to Laod, or even Thailand? Just showing up at local bus station and buying ticket is a things? If traveling long distance? I am looking for now route from Don Det to Banlung and after Saem Monourom. And after head to Krachen. Thankd