TOURIST VISA
Entry visas to Viet Nam can be applied BY POST or IN PERSON (by the applicant or anyone on his/her behalf) at the Embassy.
BY POST (Check list): Original passport, form + one photo, visa fee in EUR (cash), return envelop + stamp.
IN PERSON (Check list): Original passport, form + one photo, visa fee in EUR (cash).
Visa form is downloaded 
Visa Application Form.doc (Word verson) or here (PDF verson).
For the USA passport, the minimum visa's validity is up to 01-year multiple entries.
Business visa and official/diplomatic visa