@Dani ********
What's your long term plan for Thailand?
If you're here just to ride out COVID-19, and you'll return back to your native country in a few years, I suggest leaving the baby on overstay. A child under 15 years of age *WILL BE* on overstay (which may result in problems getting an education visa/ going to school, and you may have to leave with her and bounce back in), however there is no punishment or fines.
BUT if you want to extend her entry stamp, you will need the same documents too.