Just returned from Chaing Mai. Can highly recommend Huen Phen (search it out-it's terrific, lovely, and gets a bit crowded later in the evening but worth the wait for perfect northern Thai). The service can be slow and the waiters speak very little English, but they are exceedingly pleasant (as are all the Thai people, in our experience). Huen Phen was a highlight of our trip.
Also Just Kao Soy - what a treat and I wish we had Kao Soy in some restaurant in Phoenix. The N. Thai/Burmese version of Pho. But better, if you like curry.
Loved the noodle soup and pad thai (maybe the best I've ever had) in the unnamed Chinese restaurant (yes, that's what it's called, even on the tourist maps) across the street from the Chaing Mai Plaza Hotel, but the dim sum were only average.
Were surprisingly pleased with our meal at The Whole Earth, and Indians from our trip declared it "outstanding" for the vegetarian indian options (they returned twice in three days!).
The Wok was an unexpected find, as we were trying to find Huen Phen at the time, but gave up and stopped here for dinner. A delightful surprise of good food in a garden setting.