did it ever occur to you that the person at te embassy misspoke or you misunderstood It is clearly stated in the guidelines to be out of the country while applying/waiting for approval for the DTV
Even Bangkok bank won't open an account based on DTV these days and there are no others that will. Chances are if you are not laundering money or other suspicious activity within your account you will be fine
There are loads of people on this site ( not US veterans) who can answer this for you or you can read the details on you Thai visa embassy site. You will need to be over 50, arrive with a visa from home ( non O) open a bank account with 800K Thb, season for 2 months, go to immigration and apply for a 12 month extension based on retirement. Then you can start depositing 65k Thb every month for 12 months for the following years extension. Where the money comes from makes no difference in Thailand as long as it is an international transfer and shows as such