Custody Query - Any Advice Would Be Appreciated

Hi there.

I know that any information would mostly be either opinion, or to the best of someones knowledge, but thought I would I ask the question anyway. And please let me know if I have put this on the wrong forum, as I am very new to posting on any forum.

I am currently in a relationship with my girlfriend who lives in Indonesia. She is separated with her ex boyfriend from the UK and they have a child together. She gave birth to her son in Malaysia. They have never been legally married, yet he lied on the forms to say they were married for their childs birth certificate. So the birth certificate has both their names on it, and states where their son was born. They lived in Malaysia for a short period of time, and then moved to an Indonesian city where he worked, and they lived together also for a short period of time.

During that time, he was forever cheating, treating her like absolute trash, and physically assaulting her (she has the photos to prove it) She moved from the toxic relationship back to Indonesia to live with her parents and her son to get away from the relationship. He has threatened her numerious times that he will come take her son away from her and take him to the UK.

Her son now has an Indonesian and UK passport. He has threatened her to say he has "legal documents including from the UK to say his son is a british citizen, and malaysia where he was born". (his words). He believes that he has full rights of custody of her son and tells her that he will come and take him away.

Believe me when I say, this man is a compulsive liar, he is a dangerous individual and I believe he has full potential to cause harm to either her or her familly. He lives currently in Indonesia on a working Visa in a city not far from her own. She is wanting to move to another city to live with me and her son. She is always cooperative, always allows him to see or talk to their son whenever he wants, and has stated on numerous occasions that the relationship between him and his son would never change.

Yet he is completely uncooperative, tells her what to do, threatens her with numerous actions, They have been living apart for over 3 years. Their son is currently 5 turning 6 this year.

She is an amazing mother, full of love and support for her son, she never says bad things about the father in front of her son, and wants them to continue seeing each other in the future. But this latest threat I believe ie because he might feel he is losing control over his son, so his only answer is to take him away. As a boyfriend, I would never stop him from seeing his boy. The support that he sends is absolute minimal when you understand what kind of wages he is actually learning (around 600 Aus Dollars) per month. (I also understand that at least he sending something)

I guess what I am asking is, does he really have such custody over his son? If they are both living in Indonesia and they are not married, or never been married. What would any of you do in this situation? I 100% will not be walking away from this relationship and will give her all the support I can offer, as she truly is an amazing woman and terrific mother.

Any advice in this situation would be great. Thanks so much. And apologies that my first post is dramatic.