I was thinking of going across to Nong Khai and taking the border/river roads.

Any tips on roads like Route 2195?

Is it worth the obvious extra time that would be taken from a scenic viewpoint? Any military hassles?

I'd probably be going from Chiang Rai and bypassing Chiang Mai but the basic route to bypass Phitsanulok would be the same.

Have not driven that road but should be interesting. My experience on roads if they have one number ( Highway 1 or 2) for the highway they are good. If two numbers (Highway 11 or 12 OK to good) Three number (Highway 118 or 214 OK to good) Four numbers ( Highway 2195 you well need new suspension when you finish).

The road that goes past my house, Route 1121, is excellent; so that shoots down that theory.