What are the quarantine requirements for returning to Chiang Mai after an international flight?

Hello. I am trying to fly Chiang Mai, Edinburgh, Chiang Mai. There are flights available on at least three airlines. Unfortunately information is non-existant on how quarantine would be done on the return trip. We have called everywhere to get information but we are becoming more and more frustrated. If any one has flown into CM on an international flight please advise or direct us. Thank you!