I want the full custody of my son, is annulment the answer?

I am married for three years now and currently working abroad. i want to file annulment against the father of my son. if in case the annulment is approved, will i have the full authority over my son even if i am abroad and have my mother as the legal custodian? i have already consulted lawyers, but i want to hear it from those who have experienced the same. thanks.