it'd not that hard I have brought my thai wife here to live same year we married, first on tourist visa then convert to temporary residence while here and can work, get Medicare card while waiting. There must be financial issues or some concern about the lady by authorities in your case, or some other complications.
She cannot recieve your aged pension after you die..... sounds like she is not an Australian citizen.... you would need to being her to Australia for a few years on the right visa to sort our Aussie residence/citizenship as I am doing with my wife now. If it's a private pension/super then of course you can leave it to her.
I advise making strong "ties with thais" in the industry and working with them. There is a need for foreign expertise in this area. I would.not advise trying to go it alone, even if you somehow manage to succeed without local connections, you will likely be contravening thai law in various ways.
Spend time making friendships with farm.owners, many of whom also have shopfronts. Get to know the employment and visa law well and of course keep an eye on the silly political situation around this as you say you are.
It's an agent scam. I am also an Aussie who lives in both countries. Take your Aussie bike license with you and it is very easy to use that to obtain a Thai license with just a simple colour blindness and reflex test in a couple of hours. No agent necessary and very cheap. After first license of a year you then get a 5 license which I have. Car license is separate and just as easy
PR is what you can obtain after 3 years working not citizenship.... that's a whole different and much more difficult and lengthy process that you probably wouldn't want to do anyway.