No, it’s still possible to apply for Non O visa while on a visa exemption, get assistance with opening a bank account, place your own 800K baht and get assistance with forms and the immigration completely legal without bypassing any formal regulations.
Normally you’ll need to provide a copy of the original documentation used as the basis for income verification at the embassy. As last year's tax return or annual statement from your pension provider. Formally you’re not obligated to transfer or keep any funds in a Thai bank account as long as you’ve got a affidavit letter.
If you arrive on a 90 days Non O visa, you still should be able to open a bank account yourself although you might have to visit several branches. And you can move where you want after you’ve done your first extension. The main requirements between the immigrations is still quite equal.