Nan is top dog for sport bike riding in North Thailand.
And the Doi Poi Phukha loop with Routes 1256 & 1081 are the greatest ride 'n loops in the North I reckon.
The start of R1256 from Pua
On the way up into the clouds
The road used to end before the famous Chomphu Phukha Tree & Lookout.
Then they cut the rest of the road through to Bo Klua where the old salt wells are.
Huge culverts were built under the road to help drain the rain water in the wet season. Under the road you almost cannot see these or aware they are there, but you can just pick them out heading down /upon the Bo Klua side, once you've crossed the ridgeline by the Chomphu Phukha tree. Check em out, because without these the road would never survive.
Once you'd done the Doi Phukha Loop, the other highlight of Nan used to be riding across the suspension bridge
Photos from the late 80s / early 90s.