What are the requirements and costs for obtaining a retirement visa directly in Bangkok, excluding Pattaya?

The post inquires about the process of obtaining a retirement visa directly at immigration offices in Bangkok or elsewhere, excluding Pattaya. Commenters note that a Thai bank account with a minimum balance of 800,000 baht is crucial unless an income affidavit from an embassy is available. The costs mentioned include 2000 baht for the visa and 1900 baht for extensions, while proof of address can be provided via the TM30 form.