Close to the Myanmar border. We went there at (Western) New Year, knowing that Chiang Mai would be mayhem, so 'escaped'. The bus driver on the way there, was abysmal. Even before leaving CM on a flat road his accelerator use, surging then falling back, was enough to make me feel queasy. There are reportedly 1864 curves on the road, and i was a bit sceptical about how that was calculated, but clearly the point to note was that travel sickness might be a consideration. In the end, I didn't get sick, although two others on the bus did 'woof their cookies'. The trip home, with a reasonable driver, was good, no nausea, no people being sick. So, when going to Mae Hong Son, pick your driver!