For getting visa on arrival, aside with the visa approval letter, you are required to fill, sign and attached a recently taken photo of your face on the form NA1. See Photo guide.
You can download this form to complete it in advance to save time on arrival. Vietnamese-visa-application-form (Form NA1)
Note: If you do not have time to prepare those photos before your departure, you can ask the office taken a photo for you with the price around $2 or $5.
Citizens of ALL COUNTRIES in the worlds are eligible to apply for Visa On Arrival Vietnam. Unlike Visa On Arrival of some countries, Visa On Arrival Vietnam required applicant obtain a visa approval letter (also called pre-approval letter) before flying to Vietnam to pick up their visa upon arrival at the airports.
The landing visa counter at international airports of Vietnam open 24/7 for your visa on arrival. Please remember to print a copy of your approval letter and bring it with you for your trip to Vietnam.
In most cases, a passport scan is not required. However, sometimes the Immigration Officers need to verify the information you provide, you are required to send them a scan copy of your passport.