Is there a reason you are applying for the non-OA visa? The VAST majority of people don't want the non-OA visa, they want the non-O visa that they will then extend annually in Thailand. The non-O doesn't have any of these requirements except for proof of funds. No insurance, no medical check, no criminal background check.
As far as your questions, if you want to use your own insurance then your insurance company has to fill in and sign the form. There's about a 0.
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% chance of that actually happening, which means you have to buy an insurance policy from the list of companies on the approved embassy list.