I agree, we have always bought travel insurance when we left Australia to holiday overseas, your insurance in your home country only covers you when your in your home country.
I have seen and heard of so many people get into trouble when there had an accident whilst out of the own country
We had a 0A visa from Australia now on a OX visa from Australia.
You must have 12 months insurance if you want to stay in Thailand for a year, just before your 12 months is up you leave and go to a county close by we would go to Singapore and then come back on next flight didn’t leave the airport you don’t have to stay overnight also your first 12 months you can come and go all you like, second 12 months if you leave and want to come back you need a to buy a reentry permit to come back in.
You do not need to prove to immigration in Thailand how much money you have in the bank.
Sort out your insurance with your insurance company and get the other 3 months.
If it is a recovery letter signed by your doctor stating that you have had covid and have recovered with the dates you had it and recovered from it.
Then yes you need it and at the airport they will ask for it and put it on your file, that way if you test positive they have a record, also show it to your hotel.
Make sure you have a couple of copies of it.
Also for peace of your own mind test yourself using rat tests a couple times before you leave to fly to Thailand.
We haven’t had covid but still tested twice to make sure before we flew to Thailand
Also it’s a lot easier and faster if you have all the documents you need to enter Thailand printed out and put in the same order as how they have it on the Thailand pass. It is a lot easier than using copies on your phone and faster