Restaurant of the Vegetarian Society of Thailand, Chiang Mai.
"Vegetarian Food Club of Thailand" on Google Maps. It's not a "club". The Thai name, ชมรมมังสวิรัติแห่งประเทศไทย สาขาเชียงใหม่, is best translated into English as the Chiang Mai Branch of the Vegetarian Society of Thailand.
Update: The restaurant has remained closed since the start of the Covid pandemic. Even after the end of the Covid pandemic, the restaurant has not yet reopened (as of 23 May 2023), but grocery sales are back in operation.
Take-away food has been available since June 2023, but the selection is modest.