yes I think that's the case Graham. I haven't needed to open a new account yet. The recent changes at Bkk bank might force my hand and encourage me to change after my next extension.
I bank with Bangkok Bank and moved provinces a couple of years ago. The new province bank refused to let me transfer my account, but when I extended my visa they provided me with the necessary paperwork in about 10 minutes. This kind of thing obviously varies from branch to branch, but this is my experience.
If you think about it, the visa process is very logical in that you should apply for the correct long term visa (retirement/marriage etc) before coming to Thailand. If you do that you can open a bank account and extend your stay.
If you arrive as a tourist and decide to retire here afterwards, then obviously it's going to be more difficult for you and possibly involve having to pay someone to assist you.
I think the problem is that Thailand has been very lenient in the past allowing people to open bank accounts and apply for visas, but this has been abused by criminals and they have quite rightly tightened the rules.
you don't need a company, it's very easy to extend in Thailand. When you apply for the non O you do it online at the Thai Embassy in your country. The system is a bit clunky, but you can't really get it wrong, just provide the information they request. You use your banked money at home to apply for the non O. Once in Thailand, to extend you need to deposit 800,000 baht in a Thai bank. You cannot do the combination method at that stage (not sure if any office actually accepts that method anymore), but you can transition to the 65,000 baht monthly method for the second year extension.
Have you considered getting a non-O based on being over 50 before coming to Thailand instead? It's probably the easiest visa to get and means you can open a bank account when you get here, so that you can extend your stay for a year. You can change it to a marriage extension the second year. Many people never bother changing to a marriage visa/extension (myself included) as it's a more complicated process.