Gary
The Pai - Wiang Haeng track is on my Mae Hong Son loop guide map & its one of the rougher ones in North Thailand.
Something I would not normally recommend especially on your Transalp 400?) unless you were an experienced dirt rider.
Its a few years since I have been down there, but most reports indicate that it's still a "toughie."
But having said that, give it a go & let us know how it is, it might not be so bad.
AND PLEASE dont forget to look me up, when & if you are in Cnx.
I'm doing the MHS loop starting tomorrow, so if you see an Africa Twin on the loop Tues - Wed (- Thurs?) that's me.
Davidfl
Keep the power on