Is there an additional waiting period for renewing a marriage visa in Thailand after the initial extension is granted?

Yes, there is typically an under consideration period for the marriage visa extension, just like there was for the initial visa application. After finishing the under consideration process and completing the home visit, your extension application will likely be sent to a larger office for approval, which may lead to an additional waiting period of 30 to 60 days if those offices are busy. Once the extension is approved and stamped in your passport, you will be able to stay in Thailand until the next year, although you will still need to submit 90-day reports.