Can I obtain a Thai visa as a father of a Thai citizen child if I am not married to the mother?

In similar boat but want to know they other way bringing them to Australia

You can get a year-long, multi-entry Non-immigrant Type O visa from the thai consulate in Penang Malaysia by showing the birth certificate with your name on it, the mother's thai i/d, the house book listing and 400K baht (or the equivalent) in a bank account in your name (it doesn't have to be in a thai bank). This visa requires you exit/re-enter the country every 90 days to get another 90 day stamp. You do that for the whole year the visa is valid for. You can get 15 months of stay (in 3 month increments) out of it.

That is the ONLY consulate you can get that visa from in S/E Asia. All the other consulates in the area will only issue a 90 day, single entry Non-O visa.

Unfortunately because you had the child out of wedlock you cannot get any yearly extension based on supporting children from the immigration office inside the country. That's because when children are born out of wedlock the father has NOT parental rights. (NO matter if your name is on the birth certificate or the child has a passport from your country) 100% of the parental rights are granted to the mother.

The only way to get recognized as the legal father is to go thru family court and get recognized that way. Once you are recognized as the legal father and granted parental rights you can then use the child as the reason to get a year-long extension of stay inside the country at the immigration office.