No, you do not. From 24th August 2014, the Immigration Dept temporarily stopped granting 6 months of multiple visas. Therefore the maximum length you can apply for is a 3 months multiple visa. Those with a 5-year Vietnam visa exemption certificate are permitted to stay in Vietnam for a maximum of 180 days per visit.
They can extend their visa in Vietnam if they want to stay longer than 180 days without leaving the country. The extended period can last up to 6 months.
The visa exemption certificate is valid for up to 05 years and expires at least 6 months before the holder's passport or equivalent paper expires.
If you wish to research more about Vietnam visas, particularly Vietnam e-Visa (visa electronic), just access the Vietnam Immigration Services team, we are ready to support any questions and requirements.