Even though I have only had my Non B extension for three months I was asked by the OP for a copy of my work permit. Having just traveled for 24 hours and little battery and just connecting back to AIS it was not the best timing.

This is the first time I have been asked for a copy of my WP in over four years. Anyways after two different OPs I found a picture and was stamp re-entry. And asked if I speak Laos five times. Smiles everywhere. 

I'm confused. Is the "OP" an immigration officer?

Not sure what having a non-B extension for three months had to do with it. What were you on during the four years you mentioned?

It is not unknown and is to catch out people that don't cancel their extension of stay when their job finishes.