Can I add my children as dependents for a Non-O retirement visa in Thailand?

Now you are not under any time pressure, as your kids will not facce any penalty. Do your non o visa and then when are school holidays or when it's good for you you can visit a consolate or even you can do a evisa for your children and make a border run

They are correct, you can't apply for Non-O visas for them in country because they don't issue in country Non-O visas to family members OR foreign spouses of "retirement visa holders", it's not a reason to get that visa inside the country

It seems that you haven't even applied for the Non-O visa yet 😕

You have a three step process to get thru before you can even start thinking about your children's visa/extensions

1 - Apply for the 90 day Non-O for 2000baht

**Wait the under review period that your immigration office has

2 - Go back to get the Non-O and new 90 day stamp inked in

**Wait until you have 30 days or less left on your new stamp

3 - Apply for the year extension fro 1900baht

AFTER you get your year extension you can go to a thai consulate in the area and apply for a 90 day Non-O visa for them. They'll get stamped in for 90 days and when they have 30 or less left on it you go to the immigration office and they get matching extensions as being family members of someone on a longstay visa/extension.

That's the only way you're gonna pull it off piggybacking them on your visa/extension.