I know mini van rides only from visa runs, a couple of years ago. I never felt well. Today I avoid them whenever possible. Every week you see news reporting about horrific accidents, mostly caused by speeding or sleeping drivers.
You may try the Thai Embassy in Savannaket for a new TR visa, if you had only one TR plus extension yet. Make sure, you meet all requirements and probably it would be better to stay in Laos for a couple of days before going to the Embassy.