Can I extend my visa on arrival at an immigration office in Bangkok?

A visa on arrival generally cannot be extended. If you are referring to a visa exempt status, you can potentially extend it at the Muang Thong Thani Temporary Service Center, which operates on a first-come, first-served basis (limited to 300 applications daily). If you specifically require an extension related to COVID, it's suggested to go to the Chaeng Watthana Immigration Office. Additionally, ensure that you have the TM 30 form from your hotel, as it may be required for the extension process.