But there are some exceptions:

Only citizens of certain countries can visit Vietnam without an entry visa. They include:

• Most citizens of ASEAN member-countries: Thailand, Indonesia, Singapore, Malaysia, Cambodia, and Lao citizens do not need a Vietnam visa if they are visiting the country within 30 days; passport holders from the Philippines do not need a visa for 21 days; Brunei passport holders are not required to get a visa to Vietnam for 15 days, Myanmar residents do not need a visa for 14 days. They could apply for popular passport type with return tickets. Citizens of  Timor-Leste are required Visa Vietnam.
• Passport holders from South Korea, Japan, Russia, Belarus, Italy, Germany, Britain, France, Spain and the Scandinavian nations (Norway, Denmark, Sweden, and Finland) do not need a visa to Vietnam if they intend to stay in the country within 15 days. They could also apply for popular passport type with return tickets.
• All other citizens are required to get a Vietnam entry visa (issued prior to departure by local consulates or embassies) or a pre-approved letter for picking up an entry visa (issued on arrival at Vietnam's International Airports) at the airport. Both are supplied before arrival in the country.

Other Exceptions: 

• No visa required for travel in Vietnam for less than 90 days or several visits within 6 months - Citizens of France holding valid diplomatic or official passports. 
• No Vietnam visa required for travel within 60 days - Citizens of Chile holding valid diplomatic or official passports. 
• No  visa vietnam required for 60 days/time with  APEC Business Travel Card (ABTC) Holders from Asia-Pacific Economic Cooperation (APEC) member economies 
• Foreigners and Vietnamese nationals bearing foreign passports who enter Vietnam through an international border gate to travel to Phu Quoc Island and stay there for less than 30 days will also be exempted from Vietnam visa application. Passports must be valid for at least 45 days. After arriving on Phu Quoc Island, the Vietnamese immigration department will be responsible for issuing visas on the spot if visitors want to travel other localities or stay in the island for more than 30 days.
• No visa required for Vietnamese overseas for less than 90 days staying if they are holding Vietnam visa exemption certificate.