the 20 privilege visa is significantly more than 1 million baht. The Non O retirement visa is legally a long term visa. The DTV is a short term visa as you can't actually stay in Thailand for a year ( you must leave ). Maybe banks are giving DTV holders a very hard time opening accounts.
There is a 10 year ( really 5 + 5 ) LTR but I can't get health insurance and having to tie up $100,000 USD for 10 years in Thailand will cost me significantly more than the 1.5 million baht for the 10 year privilege visa
Even if I let my non O retirement visa expire because I left Thailand, once you have a place and a bank account, it's straight forward to go to immigration and get one.
Honestly, just get an agent. You only need them once to open the bank account. From then on its pretty easy. BTW, he will need a TM30 from the girlfriend if she owns the house.
Banks have been getting a hard time recently with mule accounts. You need a long term visa and CR to open a bank account. Which is a problem since to get a Non O retirement visa requires 800,000 in the bank for at least 2 months.
Strangely Bangkok Bank seems to be much more strict and wants a separate account just for the 800,000 and they wamt it in for 4 months or the account frozen for 4 months before they will issue the letter to immigration. It's time for my annual extension and it looks like I'm going to Bangkok Bank to open a second account with them tomorrow.
You need to do a non OA in Oz, you will have to get health insurance, but once you have it, you should be able to open a bank account in Thailand for the 800,000 baht