Can I extend my 90-day Non-Immigrant O visa in Thailand online for another 30 to 60 days?

These are the common found requirements for the 60 day family visit extension of stay at your local Thai Immigration office for 1900 Thai baht. Be sure to have a TM30 address registration on file with Thai Immigration office.

Ok

Yes just go local immigration and apply 60 day extension.

nope you can't extend it online and you can't get a 30 day extension either.

What you can do is go to the immigration office that serves the area where you stay and apply for either a year extension based on marriage (by meeting the proof of funds 400K baht in a thai bank account in your name only for 2 months before you apply)

OR

you can get a 60 day extension based on visiting thai family one time.

Those are the only two extensions you have available to you