@Bob *********
I personally know an agent who has an agreement set up with the Immigration Office and the bank. As long as the applicant is using his own funds, the process is fully legal.
Immigration allows to apply for the 90-days Non-Imm-O Retirement Visa, yet without the existence of a Thai bank account.
Immigration writes a receipt of the 2000 THB application fee. And the bank will accept the receipt as proof that the applicant is in the process of getting a Non-Imm-O Retirement Visa, and will allow the applicant to open a bank account.
As soon as the account is opened, the applicant transfers a minimum of 800,000 THB onto it.
With this proof of a deposit, after a delay of 14 days, he re-visits Immigration and will receive the 90-days stamp (starting on the day he applied for the "change"