Thank you all for the contributions but the OP has the answer he needed.

You take both passports and show them to the Immigration on return in Thailand. You get stamped into your new passport. To transfer the stamps you need to visit your local immigration office after return. The Thai Embassy does not provide this service.

Talk to the hospital staff and get a letter that she is unable to travel based on medical reasons, with that letter and her passport you can apply in her name for the Extension of Stay, with a maximum of 90 days at the time.

Hope she get well soon.

Yes and that is based on working in Thailand which you are not allowed to do for a week as your Work Permit is expired, you need to organize quickly a new work permit or cancel this stay based on working.

It must be a big stamp like this example but with the date 15 sep 2022.

I deleted your picture as your passport number was visible

@Kinga *****

So if you look into your passport, you will see a big stamp with in line 2: Extension of Stay permitted up to xx/xx/xx

What kind of stay is stamped in your passport?

Did you enter Thailand and got 90 days of stay based on buying a Non Immigrant B visa before you made your way into Thailand?

Is this a conversion made by the local Immigration Office and you got 90 days of Stay?

Please do not comment about lawyers/accountants.

You can send a picture without personal details by PM

@Nepali ******

That is the same, you can apply for the Extension of Stay based on unable to travel but have a plan B ready to go abroad, apply for a new Non Immigrant O visa and later the Extension of Stay.

If you are on an Extension of Stay, be aware that now the Work Permit is expired you need to cancel this Extension of Stay because you are not longer working in Thailand.

@Kinga *****

No, there is no way to predict how lenient a random officer can be.

If the branches are connected it will be mentioned in your work permit that you are able to work at all these branches.