Looking through the comments here, as an Aussie I have to agree with the sentiments of my compatriots. For your situation the OA is far and away the best visa to suit your strategy.

I'm 54, so I don't qualify for the Super Account advantages, although I can access my funds at 55, but these would still be taxed at 15%. As I spend about 3-4 months each year back in Aus working, I'm still able to contribute to my Super Fund, and I'm estimating by the time I'm 60 when I can access it tax-free, it will have grown to around $560,000. Even at a very conservative estimate of 6% return, this would still net me more than enough to support the 65K baht monthly transfers, without even touching the capital amount.

I've been on OA visas since I turned 50, and cannot see the advantage of the non-O which is clunky 90-day visa, requiring a visit immigration to get a year, and put 800K baht in a Thai bank account deal. I've been virtually living in Thailand for almost five years and have yet to visit an immigration office, and I'm happy to keep it that way. I get a new OA each time I'm back in Aus, and on one occasion I did do the border-bounce to get the second free year. At this point I haven't started the 65K baht transfers but this will come within a few years, as I wish to get into the rhythm well before I turn 60.

Some people are frightened of insurance, but I'm a firm believer in it. I've never set one foot outside of Australia without insurance. The cost compared to the potential benefits is negligible.

Good luck with your endeavours!

There's a limit to any study course you do in Thailand, and there's also a minimum number of days and hours you need to attend. I'm of the understanding (but check with the schools that can assist with visas) that the maximum for Thai language is two years, and unless things have changed you need to extend every 90 days, at which point you will be tested in your language proficiency by immigration officers. I believe you can also get one year on Muay Thai. I'm sure there are other courses which would qualify. I read of a Thai cooking course, but you'd only get 90 days on that. Another option is to study Buddhism, living in a temple, but you'd have to forget about going to night clubs! 🤣