The visas allow holders to stay for up to 90 days.
Since April 2020 South Korea has only been granting short-term visas for people visiting the country for trade, investment and humanitarian purposes.
It now allows quarantine-free entry but requires visitors to take a PCR test within a day.
South Korea had become a favorite tourist destination for Vietnamese before the pandemic.
In 2019 over 550,000 visited the country.