We need a new birth certificate for our 8 y.o boy. Where in CM around saraphi can this be done? I remember when he was born we went to an office around Nong hoi but can’t remember where exactly. 
 

We will then need a MOFA stamp. Is that only at the 700 y.o stadium?

I believe birth certificates can issued by your local Ampur office.
I would expect it to be easier at the Ampur that the birth was origionaly registered at.

As with anything at Gov offices,  a lot will depend on the specific person you are dealing with.