In theory yes...
However in another thread referring to Laos from @BrandonJT ...
"They're not forcing you to stay. They don't hold your passport. But if you leave they can cancel your application without refund. Multiple reports of people being asked for a follow-up proof of location like a letter from hotel manager stating you are still staying in the country, and even saw a report of someone being called into the embassy for an interview after 10 days"
Also Tod Daniels pointing out similar info.
Personally don't think would be issue with Saigon however given the approval should be ~ 5 days I don't see reason to travel. Up to you..