Yes, it's amicable. We were married in Thailand. We just use the standard forms of the Amphur. My mistake was to visit immigration by myself. I belief it might have made them think I am planning something behind the back of my wife. They were "not amused" by my questions.
sri racha. Maybe they were thinking that I was just planning to leave my wife, and I was using them to secretly prepare my future. They seemed to be upset that I had not officially divorced yet. They said to me to get a divorce first and then to come back to ask about my situation. But my wife is fully aware and wants the divorce even more than I and wants me to stay in Thailand too.
Update: I went to immigration and asked for the requirements to extend a visa based on child support. They told me that one of the required documents is a document called คร. 11. It's a document that is supposed to show I am the father. I asked them if they were sure, since the child was born during marriage, and my name is on the birth certificate. And they said they were sure. But the Amphur told they couldn't find my name in their system. So, they could not give me that document. They also said the document was not necessary. They gave me their telephone number and told me to go back to immigration and call them. The immigration officer plainly refused to talk to the officer of the Amphur - they simply said : ไม่พูด - I don't talk (with them)
In case divorce with mutual consent, the divorce papers do mention who will take care of the child, the father, the mother or both. I also has other details like who will own what after divorce.