What are the extension rules for a Non-O visa in Thailand, particularly regarding family connections?

Not every immigration office will do it. In Trat I had my non-O and tried to get a 60 day extension based on my daughter. We had all the required paperwork, but they insisted you can't get a 60 day extension based on a child. I even showed them the page on the Thai immigration website and then they changed their tune and said they stopped doing those extensions because they had a problem one time with a foreigner. Whatever the hell that means.

@L**

most places will let you apply for an extension when you have 30 days or less left on your current entry stamp BUT Jomtien sometimes says you need 15 days or less left on the stamp you're here on now.

There is no down side to going early because they ADD the 60 days to your current stamps expiration date (so you don't lose any days going early).

Take the original birth certificate, have your child's mother go (if she can) and take the child obviously.

I'm sorry I don't have much information.

You need birth certificate lists you as a father at least I think. Other documents and requirements you had better to ask handout from your local immigration office (as you know all IO requirements are not same)

And I hope

@T**

or

@Rob***

would give you a better advice.