What documents do I need to renew my retirement visa in Thailand, and do I need to maintain 300,000 baht in my bank account?

To renew a retirement visa in Thailand, you apply for an extension of stay rather than a visa renewal. For the first extension, you need to have 800,000 baht in a Thai bank account for at least two months prior to your application, along with three months of bank statements and an updated bank book. Additionally, you will need a TM30 form, TM7 form, and recent photos. If you are married to a Thai citizen, you may be eligible with 400,000 baht instead. Subsequent extensions will require 12 months of bank statements. It's advisable to check with your local immigration office as requirements can vary.