If you have an Non OA your re entry stamp is based on your Insurance expiry date that is tied to your Visa. Non OA is the only Visa that requires health insurance for the duration your Visa.
Bangkok Air has an office upstairs. Very easy to find, just ask information. You can buy a ticket to Chiang Mai there. I just did the same thing. Got though Immigration and Baggage check at 7am. Checked flight schedules, Bangkok Air had flight at 8am. Bought a ticket at office, went back downstairs checked my bag at desk and got boarding pass, went though security and walked on an already boarded plane. Was in the air within 15 minutes. One hour flight to Chiang Mai. Have a great flight.
It’s been a couple of years since I was there. When you go through Immigration you can buy a Visa . I was told in advance to bring American dollars as that’s what they accepted. When I stood in line all prices were in Dollars and that’s what everybody ahead of me was using. This was Luang Prabang. Different nationalities paid different prices.
Doctor Morgan in Chiang Mai has a lot of Expat Clients. Contact her office through her Facebook Page. She is very busy so you will not get detailed info, but if you just inquire about your medication availability I’m sure her staff will reply.
I am on a Blood Thinner that is available in Thailand but not carried by Pharmacies. I would have to go to Ram Hospital to get it. I mentioned this to Pharmacist and she said no problem I will special order it for you. I had a Doctors subscription. She had it within 24 hours.