How can I extend my Non-O visa based on retirement in Thailand, and what documents do I need?

You can apply for an extension of your Non-O visa based on retirement 45 days before the 'Admitted to Stay' date that is stamped in your passport. To qualify for the extension, you will need to demonstrate that you have either 800,000 THB in a Thai bank account in your name for at least 2 months, or a minimum monthly income of 65,000 THB verified by your Embassy, or a combination of both to meet the 800,000 THB threshold. The necessary documents include copies of your passport, ID page, visa page, the last 'Admitted to Stay' stamp, the TM 6 Form, and a Notification of Address.