pretty much nonsense from start to finish I’m afraid. You confuse financial requirements for a non O with the financial requirements for an extension of stay.
Got my Certificate of Deposit from Bangkok Bank without any fuss whatsoever, in and out in ten minutes. Pattaya 2nd Road Branch, staff very helpful. Just two weeks ago.
A valid IDP and a valid home country license are all that’s required to legally drive in Thailand. There is an urban myth that the IDP is only valid for 90 days on entry. This is false. There is nothing in Thai law or in the Conventions limiting a person to 90 days. An IDP is valid until it expires.