What options are available for extending my stay in Thailand for one month when my multiple entry visa is valid until November 2021?

Ask for a 60.days COVID extension by January 29. You may get lucky.

There is no such extension as a 60 day COVID-19 extension for visiting family. There is:

1. A 60 day extension of stay based on unable to travel due to Covid-19. The last day to apply is January 29.

2. A 60 day extension of stay based on visiting Thai family. You can get one extension of stay on each entry. (Note: some immigration offices allow the extension once per visa).

If you have not already got the extension of stay based on visiting Thai family, get that extension.