Upvote:1
Sounds like you need to make a 'Visa run'.
Pre-arrange your "Visa on-arrival" like you did with you previous multi-entry, depart the country and then return.
Another option could be to depart and then work your multi-entry through a Vietnamese Embassy, that way you can get the Visa put in your passport before you fly back to Vietnam, but this might keep you out of Vietnam for a week or so.