UK too. What is so amazing? Not everyone can afford to buy the latest expensive smart phones. Customers with contracts can have the latest expensive but 'locked' phone every year, which otherwise they might not be able to afford or have to buy. It seems to be good for companies and customers.
If you travel to Thailand on a 90 day 'O' visa for retirement, the 800k needs to be in the bank for 2 months before extension is applied for. 800k must then remain in the account for 3 mths, after which a minimum of 400k thb must be maintained until 2 or 3 mths before the extension is renewed. (Im not sure which). Surprisingly it seems that if you enter Thailand visa exempt (or a tourist visa I think) you can then apply for a 90 day 'O' visa (1900thb) and the 800k only needs to be in the bank on the day of application. (Check Asean Now visa forum for confirmation of this).
Common sense would dictate that, in such circumstances, a 2nd test could be requested, and paid for if necessary, in case of a false positive? Oh wait, this is Thailand. No common sense in Thailand.
I received a certificate with a QR Code in Udon Thani when I had my booster in January. On the certificate which is in English and recognised by the UK and EU, are spaces/lines for 3 doses. You should get the same for your 2nd dose as international certificate parity is being/has been agreed and I would think this would include Oz. Ask them to also enter your 1st barcoded dose on the certificate. U can then scan and upload the certificate as per your government website's requirements. Things may now have evolved and you might be able to get the certificate emailed to you to upload but given Thailand's obsession with paperwork I somehow doubt it.....Good luck.
If applied for in the UK (like all other visas to enter Thailand) insurance is required to cover its 90 day duration. But if applied for within Thailand and when extended thereafter no insurance is required.