What paperwork is needed to extend a tourist visa in Thailand for my grandmother?

As

@Da***

correctly stated it's nearly the same paperwork as you submitted for the 30 day 'regular' extension. So just head back to your immigration office with that stuff and they'll give you the extra forms :)

You’ll need this stuff. Not all offices have the same requirements so it may be slightly different depending on which of the 70+ offices you use.

A copy of your passport data page (signed),

A passport photo,

Proof of filing a TM30,

A copy of your departure card (TM6) (signed)

A copy of your latest entry stamp (signed)

A copy of any previous Covid extension stamps (signed) (Phuket requires this other offices may not)

In Phuket they require the copies to be in portrait not landscape. This means the top of your passport aligns along the shorter side of the A4.

(Other offices may not be as pedantic)

A filled out TM7 (application form for extensions) - the form doesn’t have a space for your email or phone number but just write it on the back (page 2).

A filled out STM2 (acknowledgement that you understand the rules for overstaying)

A filled out “I don’t want to leave because of Covid form” - I have no idea if it has an official name or number.

And 1,900 baht.

The forms are available at your local office. Most have places on site or nearby that can do the copies and photos.

Same process as the 30 day extension she had before plus two extra forms, one to agree with overstay rules and one to give a reason why you need this extension, all available at your immigration office