I think that your regular doctor will be aware that you do not have any of these, my doctor in Australia just wrote out a certificate for me, no testing required
I got my Visa in Pattaya using Key Visa, it cost me 29,000 baht. I did have the money required in a bank account. If you do not they can help organise this for you.
You can but it will cost you, better to go to Super Rich in the basement and change enough to get by. Super Rich in Bangkok has better rates than the airport
My daughter has Thai and Australian passports. We typically enter Thailand on the Thai passport and return to Australia on her Australian passport (my wife does the same), a few years ago we went to Thailand and I neglected to check the expiry date on her Thai passport. Nothing was said when we arrived however when we went to return to Australia she was not allowed to leave because you have to exit using the passport that you entered on.
We were not allowed to use her Australian passport. I was told that a Thai citizen can enter without a current passport.
I had to return to Australian and get all of the required paperwork (birth certificate etc) couriered to Thailand. It took two weeks and she missed school and my wife missed work.
Isn’t it reasonable to understand that you were granted a marriage visa because you were married? Also once you are no longer married then that visa is no longer valid?