It is NOT an Extension, it is NOT an additional extra days.
IF your application is NOT approved, you get a stamp in your passport and 7 days to pack your bags and leave the country. These 7 days start counting at the moment the stamp hits your passport.
IF your friend already visited Immigration Office for a new stamp with the text Extension of Stay permitted up to xx/xx/xx, than this stamp has to be cancelled by your friend on the last day of working. This can be done in advance, your friend can apply for a new Extension of Stay if your friend can meet any of the requirements, otherwise the new application will be not approved and your friend will get 7 days to leave the country. Make sure to tell your friend that the work permit must be cancelled at the last day of working at the Ministry of Labor.
Ask your friend what you call a Non B and Work Permit.
IF your friend is in Thailand during the first 90 days from entry, your friend can stay until the last day mentioned in the stamp Admitted to Stay xx/xx/xx.
Your friend can not apply for a tourist visa inside Thailand.
Normally you can apply for the 1 year Extension of Stay based on marriage with a Thai National during the last 30 days of your current stay.
If you like to use the monthly income it must be:
OR 40.000 Thb as a foreign deposit into a Thai bank account on your name for at least 12 months prior application date
OR 40.000 Thb income from working inside Thailand shown with payments of SSO and TAX from you and Thai staff from the last 3 months, also your work permit is needed.
When you show up with a new passport and the letter from your Embassy, your current Extension of Stay will be transferred from the old to the new passort.
It is a transfer, not a new applicaltion which will give new dates.
You are on an Extension of Stay based on being over 50 years of age which expires in Jan 2023.
If you like to apply for a new Extension of Stay during the last 30 days, your new Extension of Stay will be until the expiry date of the passport.
You can not get permission to stay inside Thailand without a valid passport, if you want a full year Extension of Stay you need to apply for a new passport.