Nort Thailand is biker's heaven.
I have been driving in north Thailand twice, -07 and again this winter, total round 2500km.
Norht Thailand is all this: Thousands of curves, very good road surface (asphalt), nearly no traffic, beautiful scenery,good food, nice people and cheap. What else do you need for a good holiday?
And there is safety to travel. Even a woman can drive there :)