Khun Churn is a Chiang Mai staple. Located on soi 17 off Nimanhaemin, seating under a trademark tin roof provides an outdoor atmosphere for friendly facestuffing. You can also choose to sit indoors, but beware if it's rainy season. I've sat inside during torrential rainfall and water actually leaked from the light fixtures.
The lunch buffet, anytime between 11:30-2:00pm, is decent. Less than 100 baht for a plethora of vegetarian, เจ [jay], dishes, plus your choice of an herbal beverage. Otherwise, Khun Churn offers a vegetarian friendly breakfast menu and/or reasonably priced dinner selections. I don't think I've ever ordered something I didn't like.
notables | mushroom & seaweed omelette [หอยทอด or huay tod]. fresh spring rolls [ปอเปี้ยะสด or popiah sod]. pomelo salad [ยำส้มโอ or yum som-o]. sizzling mushroom plate. fried potatoes with garlic and cilantro. lemongrass beverage [น้ำตะไคร้ or naam tda-krai].