I guess you want to double check but for me the questions are clear even I not have experience with long term visa:
1. Copy of main page of passport
2. Screenshot of you
3. Statement of your current local government so of your city that you formally are inscribed in that city
4. Either copy of balance of your ban statement proofing you have 400.000 on that account or employer / pension/ other statement from them that you at least get from them 40.000 per month (no need to say it can be in euros but equivalence should be 40.000 in baht)
5. Copy of passport of the person (family or wife) you are going to live with
6. As clearly asked, copy of birth certificate, proof you have a kid over there
For a short term visa I had to do more (she coming to me) and especially during Covid-9 period.
I read it differently: Proof of onward travel and funds
Immigration officials in Thailand may ask you for proof of onward travel (eg a return or onward air ticket). You should make all reservations before travelling to Thailand. Some airlines have refused to board passengers without evidence of onward travel.