You can either use the Thai Consulate in Sydney or Thai Embassy in Canberra?
you do your application on line and it’s approved you send them your passport and paperwork as requested you post it all in a overnight express post and include a self addressed overnight express post envelope with your paperwork.
It only takes a couple of days and you will have it back.
The Embassy will send you an email letting you know it has mailed your passport back to you.
First two are whilst in Australia you apply for either an OA or OX visa. They can only be done whilst inside Australia.
OA is for one year plus one so 2 years just before your first year ends your fly out of Thailand then fly back in and get stamped for an extra year
OX is for 5 plus 5 years. On entry into Thailand you are stamped in for 5 years at end of 5 years once again you fly out then back and get another 5 years
Both of these you can do through Thai Consulate in Sydney
Or you can enter Thailand on either a 30 day visa excempt and get an extension on it which will give you 60 days in this time you visit an Immigration Office and get a print out of what is needed for this visa, your first things is to open a Thai bank account and deposit the money needed
Or look at the Elite Visa
My husband and I are Australians and we have been on the OA a couple of years ago and now on the OX if you would like to message me I can explain it more and can find out how friends on an OA visa did his wife as a trailing wife