Travelers coming to Vietnam must apply and obtain a visa to enter the country. There are two ways to get it; from a Vietnamese diplomatic mission or on arrival through one agency (online or offline). The visa on arrival can be only stamped in the airports of Ho Chi Minh City or Hanoi. Moreover, for all kinds of visas, your passport must have at least 6 month’s validity.
However, there are some visa exempted countries for a limited stay. This is the map of those countries and the maximum allowed length of stay for each one:
*Required to hold a passport valid for at least 6 months from date of departure from Vietnam, at least 30 days must have passed since last leaving Vietnam, and required to show a printout (computer/mobile screen not acceptable) of a flight ticket to a third country.