I don't know, obviously things like where I used to live with my wife has come from the yellow book when I relocated to a different province, That they knew about me being investigated for the suitability of being a co-carer with my partner of two small children in our household (I now take care of their children) has come from the Youth welfare office (a very detailed investigation with lots of interviews with her relatives, the children and possibly contact with German authorities as they knew of my divorce in Munich, took 3 months), I being a foreigner they probably reported the findings to immigration. That I hadn't left Thailand was apparent because I had never applied for a re-entry permit. I don't know why they should know about my son except that my name was on the birth certificate although why it should be necessary to inform immigration of his birth, he being Thai, I can't imagine. I have the feeling that they know more about us than we realize.