I don't know if it's still valid, but there is/was a form that if your insurance company accept it to sign, there are imm. offices who accept that form.
I think when you arrive on visa exemption 30 days and somewhat later y'r visa arrives, you maybe also can do an extension of 30 days first and then leave and come back. Y'r visa is 90 days valid for coming into the country. You have to calculate a bit if this maybe delivers some extra time for you.
Second part: No use in Thailand to have a joint account. When Amphur knows one has passed away, the account is closed. When officially maried or having a will, you must go to court to get a document with which you can get the money. Ofcourse when you go to the bank/ATM quickly, you can get the money, but should it be discovered, a fine and/or put back the money is possible. This is different from many countries where the account stays open e.g. to pay (automatic) bills etc.
Yes, no problem. Always take "Class 1" insurance if you are driving it. (Name owner is on the "Tabien Roht' blue book. If it is bought with a lone, there should be a copy of this book in al the papers)
Do you mean '1 year extension of stay with 800k฿ on the bank' or you still have the original visa for 90 days ?
If you are on extension of stay, you have to finish this first. After that you can use letter from y'r Thai bank with 12 international deposits of 65k฿.
If you still have the original visa, you need the 800k฿ in the bank for y'r first year extension. 1 year later you can use 12x 65k฿ for this.
If it's for you alone (Thai wife), concerning "...rather than all my income" I would say transfering a bit more than
*****
k฿ per month (40k฿ if legally maried in Thailand) as "international transfer" and not everything, is smart anyway because maybe the Thai government will enforce their tax law. So the top of y'r pension, will not be in the higher tax trance. Nobody knows exactly yet.
Yes, if you have
*******
k฿ (Again 400k฿ if legally maried in Thailand) in y'r Thai bank account (in y'r name only), thats sufficient. No monthly transfers needed.