A short while ago I did the usual visa run to Cambodia as per the 6 month requirement ( despite the fact I have a 5 year Exemption visa which is a misnomer in itself ) At the time I was advised to renew my passport as it was full of stamps with no room left for any more. So, off I went back to England, at some cost I might add, spent 3 weeks there and obtained a fresh 100 page passport. On my return to HCM, despite having my old passport with me, I was refused entry as my 5yr exemption visa did not match the number on my new passport. Needless to say that after some heated discussion I walked through immigration anyway having refused to join the rather extensive queue at the visa desk. Detained I explained the problemand to give the officer in charge credit, he took my passport, went to the visa desk and promptly returned with a 30 day visa ( $20 fixed it )
The next day I went to the ministry, explained the situation, paid a further $50 and hey presto, a new 5yr exemption visa.
My fault I guess in that I had not foreseen the problem of mismatched passport/exemption visa numbers despite having been here many years and knowing only too well that any excuse to claim more money would obviously be exploited.
I guess smiling is the best option here . .. . and a few well placed dollars of course.