Passport renewal

You need to make an appointment.

"You will need to schedule an appointment online by following the steps on our Appointment System and submit your passport application at either the U.S. Embassy in Hanoi or the U.S. Consulate General in Ho Chi Minh City.  Once you have scheduled an appointment, please print out the confirmation page for access to our office on the appointment date.  If there are no slots available in the Appointment System, please go back to the system at a later time.  Appointment slots are opened approximately two weeks in advance, and additional slots are often added, so we recommend you check the system periodically for availability."

Go to this page:
https://vn.usembassy.gov/u-s-citizen-se … -passport/

You will see the link to the Appointment System.

Click on "Required Documents for Adults (age 16 and older) to Renew a 10-Year-Validity U.S. Passport"
for the other details and a link to the passport fee calculator. Looks like it's $110.

"Bring cash or a credit card/debit cards to pay the fee. All fees are payable in U.S. Dollars or Vietnamese Dong in cash, or in U.S. dollars with the following credit cards/ debit cards: Visa, MasterCard, Discover and American Express.  We do not accept checks."