My partner and I recently had a child 2 months ago in Koh Phangan. My partner and child both have Thai Citizenship, I hold a Australian Citizenship (age 36).
We are not married.
I would like to find out if it's possible to get a Thai visa based on parental grounds for myself. Ideally I would prefer to get a multiple entry visa that can be renewed yearly. I'm not sure if nominal amounts of cash need to be shown in bank accounts. We have the money to show in an Australian Bank account, but not a Thai one.
TLDR : Answer Summary
An Australian father of a Thai citizen child can apply for a year-long, multi-entry Non-immigrant Type O visa from the Thai consulate in Penang, Malaysia. Required documents include the child's birth certificate, the mother's Thai ID, a house book listing, and proof of funds (400,000 THB or equivalent) in a bank account, which does not have to be a Thai bank. However, due to being unmarried, the father may not have automatic parental rights, and may need to go through family court to gain legal recognition as the father, which is required to obtain a yearly extension based on the child.