Is health insurance required for a Non-Immigrant O visa in Thailand, or can I choose my own level of coverage?

IF you get a Non-O visa inside the country (for any reason they issue them) there is no requirement to carry any health insurance. However IF you buy the Non-O in a thai consulate in your country before you wing your way here, depending on the reason you're getting it the consulate might require mandatory health insurance. Check the website of the consulate in your country for the reason you're getting a Non-O to see