I am on a non O (retirement) extension issued in country, which does not, when issued, have the Covid insurance requirements of an OA visa. Is proof of insurance required if re entering Thailand on this visa? I’m fully vaccinated, including booster.
What paperwork are you talking about? If you are talking about you, a foreigner, marrying a Thai lady, the cost is virtually nothing. I married my Thai wife ten years ago, we did all the paperwork ourselves, no legal agencies were involved at all and from memory the overall cost was a few hundred baht.
Kool Breez is correct. The question refers to whether you have been refused a visa to Australia in the past. Your visa refusal to Thailand is not relevant.
The only part of that I can disagree with is "filing online is quite easy". I've never been able to get it to work in 3 years, but it's not really a problem for me anyway, I'm 20 minutes from my local Immigration office. :)