Well, after reading all the comments here, I decided to take a different route today.
On the way, we took what I thought would be a shortcut, to pass through Nong Bua Lamphu
but that road is horrendous. If any of you value your vehicle, I don't suggest you take that road.
We just came back from Nong Khai and went straight to Khon Kaen, which was
pretty smooth sailing apart from a few very rough patches. As far as I remember, the road from CR to the Phrae area was ok.
Don't even get me started on the amount of stress the immigration officers put me through in the last few days.
Apart from that though, everything else is tickety boo.