rattlesnake

Hello all, There are several threads on the forum related to this matter and I have read them carefully, however I still haven't found a clear answer with regards to my issue: My son was born last year in Thailand, but due to unforeseen circumstances I was unable to attend the birth. In typical Thai fashion, one of my girlfriend's cousins who happened to be there at the time was named as the father on the birth certificate. We are currently in the process of registering our marriage and it should be sorted within the next three months. I will then be my son's legal guardian. The problem, however, lies with the birth certificate: my son doesn't bear my surname and the one feedback I got regarding this is that it can be very hard to revert. Is it really that hard to get the amper to issue a revised birth certificate if we're married and the said cousin shows up with us and explains what happened? Thanks.