we lived in thailand for 13 years and recently returned to the uk. Is my son able to return to Thailand to see his father who still lives and works over there and owns a property ?

Hi, I am married to a Thai citizen and I have 2 minor children, I have a non-O marriage visa issued by the embassy. Since this year I have not lived with my wife anymore and I moved to another province with one of my children. I've had 400,000 baht deposited in the bank for years. Can I ask for a one-year extension since my child lives with me, even if I'm not divorced? thank you