Anyone coming here for retirement purposes should get the 90-day non-O from their home country. I've no idea why people want to stuff around making the switch from a tourist visa or a visa exempt. I've never been able to figure that out
The minor changes to Thai taxation does not affect the DTA. Under the conditions of the Australian/Thailand DTA I am deemed an Australian Tax Resident, therefore only Australia can tax me on worldwide income. Thailand can only tax me on money which I earn inside Thailand, and as I'm retired that's a big fat zero. If I was earning money here, I would have to declare it on my Australian Tax return, although I would be able to apply tax credits, but that's irrelevant anyway
I still don't believe non-O visa holders will be stopped from opening a bank account providing they can supply proof of everything, such as long-term lease and passport with non-O visa