Originally Posted by Davvidd

Could be that. It happened to me once in BKK a while back when I had to apply for a visa on arrival. It was called fast track and you had to pay a certain amount officially at the counter and you get it immediately. This guy who was conducting the queue send me to the immigration officer and told him the amount for me to pay in Thai. I can understand a bit and knew the amount was more than what was official. The immigration officer told me the official amount and the other guy told him the higher amount. The Officer looked surprised but I paid the higher amount ( I think it was an extra 200 baht, 6 USD) just to get out of the queue.
So it very well could be an attempt to get something out of it. But the Vietnamese authorities are fairly strict with lowly officials.