I walked past there this lunchtime, noticed two big signs with "Imboon", and asked (in English) the lady if it was a vegetarian place. When she replied (in English) that it was, I chose three items (without rice) from the display case, and she brought me a small bowl of hot (tasty) soup when I sat down.
One plate was stir-fried morning glory with fresh chilli, one item was stir-fried bamboo with tofu and the third item, which I can't remember the name of, and which included rice noodles, basil and tofu, was just so phenomenally tasty I couldn't believe my luck.
All three items were freshly made, and at room temperature in a covered display. The total for three dishes came to 40 baht, which I thought was a good price for lunch.
I asked when they would be closing (17:00) and decided I would come back after walking around the centre. When I got back, the morning glory stir fry had gone, so I took two containers with the food I had already tried, plus a small banana leaf wrapped steamed spicy piece of tofu, as well as a fantastically tasty steamed rice triangle with shiitake mushrooms, adzuki beans and gingko nuts. It was slightly sweet, and felt like something I'd eaten in a Japanese buddhist temple many years ago...
If you're about to leave the city for a day trip or to another city/country on the bus, I'd suggest grabbing a meal or picnic in take out containers here before you head out, as well as the steamed rice triangle!
This is the first and only vegetarian place I've been to (so far) in Chiang Rai and it was very pleasant, friendly, tasty, and pretty good value for money. The work area and the display area are clean and I liked the fact they gave me recycled card containers for takeout items...