Hi I have duel citizens I came here 8 months ago to Thailand with my American husband as I am half American/ Thai. We came on an OA visa yes I as well . I have my Thai ID but not a thai passport. Once I got to Thailand I had to follow the same procedure as a foreigner. For her/ I have to leave the country with her German passport and come back in on her Thai passport to be valid. Otherwise she would still be considered a foreigner. Thailand doesn’t care if your thai and carry a German passport you are consider a foreigner until you leave the country and come back in using her thai passport. If you don’t want to do another quarantine then wait and keep doing your 90 days check in until she can leave and come back with out quarantine. I am in the same predicament . Once your year is up ( if you came in on an OA ) do a marriage visa .
with type 2 diabetic if your on medication you can buy it at any pharmacy. As far as insurance goes normally pre existing condition most Thai companies (insurance) will not cover the cost. You may pay a lot more and get it if you have the funds to do so.
Being type 2 a lot of Thai’s have it so medication is easy to get. I have type 1 insulin dependent so it’s still available for me and I have an insulin pump. So no worries on that.