You should be applying for and getting 60 days extentions of stay from any entry if you have a Thai son. Take him and his birth cert to Immigration with you when you apply.
800k transferred from abroad, no seasoning required, for the Non Imm O visa. 800k seasoned in a Thai bank for 2 months for the 1 year extention of stay.
Not many Embassys/Consulates sell the multi entry Non Imm O. Savannakhet, Laos and HCMC, Vietnam used to before Covid but those were the only two I know that did