Just to pass on to anyone in similar situation.
We attempted to get our son his Cambodia passport at the Poipet passport office (its about 2-1/2 hours away). It was a ridiculous waste of our time.
We took:
Mother's birth certificate, mother's ID card, Mother's cambodia passport, mother's document from police stating where she lived (took as she had a friend go to this office about one month ago and they requested it). My passport. I also took our oldest son's Cambodia passport and his birth certificate just in case.
When we arrived I got out my wife's birth certificate, her ID card, our son's birth certificate and my passport - as those were the documents we were told on the phone by the passport office that we would need.
First we were told that we needed copies of the Cambodia birth certificates. We were literally standing two feet from a copy machine. I pointed that out. Nope. They said we needed certified copies of the birth certificate FROM THE LOCAL POLICE WHERE MY WIFE WAS BORN. Then we were told we needed the document from police stating where my wife lives - Ok, I pull that out. Then they said I needed the same document proving where I live! I showed them my visa. Then they said - nope, the document for my wife was not ok either - she needed to go to where she is registered and get the document from there.
So at this point, I pulled out our oldest son's Cambodia passport and I pointed out that we successfully obtained his Cambodia passport with the four documents I had pulled out initially. They were very unhappy. Said everything has changed. And then the kicker - they then decided that we needed all the above AND we would have to go to Phnom Penh as they couldn't process applications from barangs. And with that the gentleman literally walked out of the office and down the street.
An entire waste of a day. Regardless of what should happen I would have to recommend that anyone in similar circumstances simply avoid that office. I think later this month when we head down to Pailin we may try stopping at the office in Battambam.