@Peter ********
a Non-Immigrant Type O-A visa has to be gotten in your country BEFORE you come here. You apply at a thai consulate, with a police background check, a medical certificate, you show proof of funds in your country and (since Oct 31st 2019) you meet the mandatory insurance requirement to get that visa.
It's good for a year from the date they issue it, it is unlimited entry and every entry gets you stamped in for a whole year while the visa is valid.
Meaning IF you exit/re-entry just before the visa itself expires you get stamped in for a whole new year (giving you two years of stay out of a visa that's valid for a year). Then you either go back to your country and buy a NEW Non-O-A visa, OR you apply for a yearly extension (just like you've done on your Non-O visa every year) and the only difference in the in country extensions between the two is that O-A visa extensions require the mandatory insurance while O visa extensions do not. They both have the same financial requirements to get the year extensions