Bringing Thai stepson to the United States

[SundaySunday 3]

I think my case may take a little longer because I am petitioning for my wife as well as my stepson.  We also have a child together who is an American citizen with a U.S. passport so that is not an issue. I will be traveling back to Thailand in a few weeks to see my family and go back to my wife's hometown. It seems the last time we went to the Amphur in her hometown, they gave her the wrong paperwork in regards to her having sole custody of her son. My wife and the biological father never married.The biological father left my wife weeks after their child was born, now my stepson is 8 years old. When we went to the Thai embassy they issued my stepson a passport but mentioned that we would need to obtain proper documentation for my stepson to travel abroad. My stepson's surname was changed within a year of his birth so we have that documentation covered. I know we will need permission from the child's father or sole custody documentation. Has anyone on this forum dealt with this issue ? We would like to go the sole custody route as my wife wants nothing t do with the child's father.