I admit I don't know if newborns are able to get a passport yet, maybe a birth certificate is ample enough
@Tod ********
?
Depending on your nationality the baby could enter visa exempt and overstay with no fines or ban. It appears you're Ukrainian, was the baby born in Ukraine? Failing that, if you apply for a DTV for the newborn you'd need to pay 10,000 baht and the primary DTV holder would submit a sponsorship letter with proof of funds in their bank account. Let's wait for Tod to chime in.