Any recommendation for a Tai Chi teacher in Chiang Mai ?

I don't know of any teachers but one way to find one would be to get up early and go to public parks and you will find people doing Tai Chi. Hang out, try to imitate a bit....they'll LOVE IT. If you can find someone there who speaks English (I'm assuming you don't speak Thai) ask them if anyone knows of a teacher. If noone speaks English then go to the next park and repeat. Finding your teacher could be the adventure of the decade!!!

http://www.taichithailand.com/

the teacher is an american by the name of Keith Goode. Been teaching for manys years. In some circles one of the best.

I took the course last year and I can thoroughly recommend it!

The course covers not only the essential Tai Chi postures, but the theory which in my experience is never covered in such detail with many excellent and related examples.

Keith is also a very approachably and down to earth person, which makes the learning experience even more enjoyable.