I had been to Bangkok hospital on my previous trip to get some lab tests. I just requested another appointment through the website and they sent me the appointment slip. That’s what I provided to the embassy
honestly it’s no different than the other items. A cooking class for a week, seminars, or a one time musical event and you get 5 year Visa😊 Keep this in mind…the Thai government didn’t create this Visa to keep people out 😊