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-19 pandemic. Even after the end of the Covid-19 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.