Vietnam is not so strict on entry visa requirements like other countries. Below is list of things you will need to know before you enter Vietnam:  

Mandatory Requirements (in case you get your visa in advance from the embassy)      
* Passport should be valid 6 months beyond intended stay    
* Vietnam visa is required  

Mandatory Requirements (in case you apply for a visa on arrival online)      
*  Applicants must enter Vietnam by air to Hanoi, Ho Chi Minh city or Da Nang.    
*  Passport must valid at least 1 month from the date of exit.    
*  Two passport photos size 4 x 6 cm (see photo specifications).    

In most case, you do not need to show the following:
* Proof of Return
* Vaccination Certificate
* HIV Examination Certificate