Been there,done that. I had an OA but that required expensive medical insurance and most only offer unnecessary International insurance whereas I was looking for Thailand only.
I ditched the OA but still bought medical insurance Thailand only ! with Bangkok Insurance,a reputable company and the premium half of what the International Policy was.
Why on earth does one need all those inclusions in International policies ,like reparatriation of body from USA ! when I'm never going there ?
If I want to go to Europe I just take out a Schengen policy for the time there ( just done, 100 euro for 2 months )
It is essential for anyone approaching 70 to get Medical Insurance as after 70/75 most policies not available.