Does the 90-day reporting in Thailand start from entry or from the extension of stay for non-immigrant O visa holders, and does it apply to children?

In Thailand, the 90-day reporting for non-immigrant O visa holders is counted from the entry date into the country, not from the extension of stay. This rule applies to children as well, although there seem to be no fines for children regarding overstay or failure to report. Many expats report that they personally handle the 90-day reporting for themselves, but often do not do it for their young children without facing any issues from immigration.