Upvote:2
I found that your concern has not been answer at all. So, I don't know whether you have been to Vietnam with your 15 days visa exemption or not. But as I know, via this link https://www.vietnam-visa.com/vietnam-visa-extension/, a visa exemption can be extended for up to 3 months. Although now, due to COVID 19, Vietnam is temporarily closed to all incoming foreigners, I hope this piece of information will help in case you wish to visit Vietnam in the future with visa exemption.