I entered Vietnam on a 3 month B3 visa in March 2013. I've left my passport with a Saigon Visa business to extend it twice for three months each since then, so I've been in the country without leaving for about 8 months.
In the past I've been told 3 month Visas can only be extended once for three months after which time you must leave and re-enter the country with a new Visa. The last time I had it extended, I expressed this concern with the business owner. He told me I can extend it through him yet again with no problems (a third three month extension) but I just have to pay more money for the people at immigration.
I'm concerned perhaps I should leave the country and try to get a new Visa rather than continuing to extend. I don't want to run afoul of the rules. On the other hand, it would be cheaper and more convenient to extend with the same people again.
If anyone has knowledge on the subject please contact me.