Can you suggest some good thai restaurant in and around Chiang Mai

For Thai food in Chiang Mai, please try both central Thai food and northern Thai food.

For central Thai food in old town area just opposite the Tha Phae Gate, I recommend ถนอม / Thanom restaurant. They open for lunch and dinner time for a few hour only.

For original northern Thai food, please try ลำดีตี้ขัวแดง / Lum Dee Te Khua Dang at V COMMUNITY วี คอมมูนิตี้ ที่สุดของชีวิต ติด ม.พายัพ on the suburb of Chiang Mai town.

Both restaurants are affordable prices.

Check out Chang Phueak north gate and try the khao kha moo (a stewed pork leg on rice dish) by the cowboy hat lady.

I like the less touristy  Siri Wattana and Thanin Market. These are 2 markets on Soi Thanin in Santitham Chiang Mai. You get a variety of foods at affordable prices. There is a range of desserts and snacks like the famous Chiang Mai fried pork rinds.

Deck 1, a quiet restaurant by the river is another of my favorites. It is located at 4 Chareonraj Rd., T. Wat Kate, A. Muang, Chiang Mai. (photo: Khao Soi):

Try this one , in Thai it's called "Hoi Ka" (hanging feet) the restaurant is on the second floor https://www.google.co.th/maps/@18.7843421,98.9818674,3a,75y,137.03h,94.13t/data=!3m6!1e1!3m4!1seTvoF4Vf_aCPMer42FRLKQ!2e0!7i13312!8i6656?hl=en

Enjoy ! 

Just returned form there. Nothing like grandma's lining up on the street at 1:00-3:00A.M. serving you amazing noodles and food on a stick for <$1. Most underrated place for food I've visited IMO. Try the Tha Phae Gate area and Nimman Boutique Resort. street areas. 

Also, Ristr8to is a must for quality coffee.