Old thread, but I have the same question currently. Recently purchases a string of SE Asian flights (various locations in Cambodia and Vietnam) directly through the VN website.

The credit card I used was lost and a new number is being issued. VN's website FAQs says the card must be produced at check in or verified with with a branch before flying.

Is this really true. I will call the office in San Francisco, but wanted to see if others had good information on this.

Thanks in advance for your help.

Info from VN's website below:

HOW DO I VERIFY MY VISA/MASTERCARD/JCB USED TO PURCHASE AIR TICKETS ON VIETNAM AIRLINES WEBSITE?

At the airport, the card holder must submit the Payment card, Passport, eTickets for verification upon check-in when it is required by Vietnam Airlines.

In case the card holder can not verify the payment card at the airport, the card holder must submit the payment card, Pasport, eTickets to verify at Vietnam Airlines branch offices before travel.

For ticket changes, the card holder is required to submit the Payment card, Passport, eTickets for verification at Vietnam Airlines branch offices.

In case the card holder can not submit payment card for verification, Vietnam Airlines reserve right not to provide service or require passengers to purchase new tickets.