Single entry or multiple entries visa refers to the number of times a traveler can enter and exit Vietnam during a certain period of time.
+ Single entry visa: you are allowed to enter and exit Vietnam once time only during your visa period. This is also called visa with single use. Once this single entry visa is used, you cannot enter Vietnam again but must reapply for a new visa. For example, your type of visa is 1 month single entry visa. It means you cannot re-enter Vietnam if you exit Vietnam after 8 days of stay even your visa is valid for 30 days.
+ Multiple entries visa: you are allowed to enter and exit Vietnam multiple times during your visa period. After getting a multiple entries visa at the airport, you can exit and re-enter Vietnam at any ports you want. However, when your visa expires, you still need to apply for a new visa.