Most countries need a visa.
Passport holders from Brunei, Cambodia, Denmark, Finland, Indonesia, Japan, Korea, Kyrgyzstan, Laos, Malaysia, Myanmar, Norway, Philipinnes, Russia, Singapore, Sweden, and Thailand do not require for a visit of 14 or 30 days.
Tourist visas are good for thirty days and may be extended after your arrival in Vietnam. Fees and requirements vary from embassy to embassy; about $50 in Bangkok and $85 in Washington, for example. A double entry visa is also available for tourists making side trips from Vietnam to destinations in Thailand, Cambodia and Laos.
A visa on arrival service is offered by various travel agents on the web. This is more of a pre-approval visa service and you may be limited by arrival dates and arrival locations. It is only available for arriving at the airport. We strongly advise you to get a visa before arriving.
Vietnam Passport and Visa Guide