Taste From Heaven has an extensive menu of many different types of cuisine, including but not limited to Thai, Indian, and western dishes. Breakfast is served all day. The whole menu is vegetarian, and most of it is vegan, too (everything that is vegan is labeled as such, and everything that is only vegetarian that can be made vegan by request is clearly labeled, too).
I've been here 3 times, and every thing I've tried has impressed me. I've gone with both vegan and vegetarian friends, and all of them adore this place as well. Vegetarians recommend the pineapple fried rice (served in a followed out pineapple!), which can also be made vegan! Their pad thai is the best in the city, and the pumpkin / coconut milk dessert is probably one of my favorite treats of all time. The prices are on par with other veg restaurants in the old city, and maybe even slightly cheaper than Aum or Anchan. The location is great (south of Tha Pae gate near Juicy4U), and the decor is nice. If you're in Chiang Mai, you MUST go here!
Cons: sometimes gets a little too busy!