Have done a search and can find no reference to this question.

When applying for an extension, what are the minimum months required to have remaining before the passport expires?

My passport expires in August next year, I am due to repeat the extension process in January next year, is it better to apply for a new passport before applying for the extension, or wait until the extension is granted then apply for a new passport and have the extension transferred to the new passport?

Thanks to those more informed than I.

There is no minimum requirement to get an extension, only to enter Thailand your passport needs to have a validity left of at least 6 months. So unlless you want to travel abroad you don't need to apply for a new passport till it almost expires. Just allow for enough time to get the new passport.

You can apply for extension of stay as long as your passport is valid at that time. When you need to renew your passport you will have to get immigration to transfer your permission to stay/re-entry permit stamps to your new passport.