Hi, 

My Thai girl is pregnant (me being the father), and when I consulted with the Thai Embassy in my country, they said I could go to immigration here and get some kind of visa for one year since I'm the father of a Thai child...anyone that has some experience on that and might know what is required?

Best regards

You will not be able to apply for a non immigrant visa or a one year extension of stay at immigration unless you are the legal father of your child by way of marriage to their mother or legitimization of your parenthood.

You can get a a single entry non-o visa that will allow one 90 day entry at most embassies and consulates without  legitimizing your parenthood. Some will also issue a multiple entry non-o that will allow unlimited 90 day entries for a year.

You will be able to apply for a 60 day extension at immigration of any type of entry to visit you child.

Info about legitimization is here. https://forum.thaivisa.com/topic/381917-how-to-gain-parental-rights-as-a-father/