@Daniel ******
. . .your question was about switching from Non-O/A to Non-O . . . . . well, once the borders open, you will be able to let your O/A extension become invalid leaving Thailand without a re-entry permit, and go for the Non-Imm-O visa based on being over 50. For this, there currently is no health insurance requirement. Tod Daniels has written up a special thread on how to do an in-country conversion from a tourist visa or visa exempt to a 90-days Non-O based on retirement visa