Single entry tourist visa gets you 60 days + 30 day extension, total 90 days in country.
Extensions cost 1900 baht and take half a day at the immigration office.
It maybe necessary to show onward travel within 60 days. For that you can buy cheap bus tickets that show a departure date within 60 days. There is no requirement you actually have to get on the bus and there is no requirement onward travel means by air.
When Covid first hit, many of us got Volunteer visas. Towards the end of covid immigration scrutinized those with volunteer visas more so than other people (so I heard).
I have a volunteer visa in my passport. I have since gotten a couple of marriage visas and maybe a tourist visa... I am not sure but nobody has said anything about it.
There may also be a difference between a legit volunteer visa and a early-covid volunteer visa.
I did back-to-back tourist visa for years. I also had a few other visas. I have had very few issues living in Thailand. I am now 49.
Many people do student visas I have not. The last I knew the big issue with the student visa was that they required people to go to class.
My recommendation would get a long-term multiple entry visa, if possible, come here, hang-out for 9 months then figure out your next steps. The METV will still require you to do border bounces every 90 days
You would still need to leave the country but you can forgo the hassle of an immigration office.
It's a bit of a gamble on your part. I made the same gamble and it worked out for me, I can't promise it will work out for you.
I started the visa process while in Thailand. I did have to show flights going into Thailand. Also, when they requested more paperwork I explained my situation and they seemed cool, they gave me the visa.
I applied for my marriage visa (eVisa) from US embassy while in Bali. You may be able to to apply for a marriage visa from the Embassy in Australia. I found Brisbane and Melbourne to be the friendliest (4 years ago).
I use bus tickets to fulfill that requirement. The last time I did that I bought a ticket from Hat Yai to Penang and I think it was $12.00.. It's been a couple of years. 12go.asia (that's a website).
The requirement is something like "onward travel reservations/tickets". A) Doesn't say has to be a flight, common misconception. B) Does not say you actually have to get on the bus/plane, just that you have tickets.