Seun Handyman you need to have a current TM.30 to do your 90 day report, yes. If you haven’t left the country you can still use the TM.30 you did when you (re)entered Thailand.
So my gf went down to do her visa extension after paying the landlord to update her TM.30 the night before. Apparently it takes a day or two to process because when she went to immigration they said her TM.30 wasn’t valid and tried to fine her 3000 baht. She ended up doing a border run to restart the clock instead.
Moral of the story is don’t put it off to the last minute like we did. Be aware that immigration has to process and formally accept the TM.30 report online before it’s “official”.
If your child is under a certain age there is no penalty for overstay, but they do get an overstay stamp in their passport. As long as they are with a legal parent/guardian that has proper entry authorization on their next re-entry then no issue.
The Chonburi immigration office in Pattaya has also cracked down on this. They were going to fine my gf something like 2500 baht for not having a current TM.30 when she went in to do her 30 day extension recently. She elected to do a border run instead to restart her clock.