30-50 kms before ck aleft turn off leads up a nice twisty road. You'll know it when you see it, a proper intersection with turning lanes etc.
Past ck keep to river side or as close to as possible. Some nice twisty back roads (sealed) before turning south to main road to Loei. Very good nic main road through hills, nice high speed curves. (Yes, I know you're on a R.E.)
Sangkhom, half way Nongkhai to ck, accomodation 200baht up.
Wat pha tak seua and waterfall 10kms or so before Sangkhom is nice. Follow river away from shallow crowded area, it gets better. Good for a dip.