Hanoi Airport layout

I have a friend that's in the process of booking a flight to Vietnam arriving in Hanoi and needs to catch a domestic flight down here to Can Tho. Times are really tight. Is it possible to arrive, clear immigrations / customs and make it to the domestic departure terminal in less than 4 hours? Already will have the visa stamp in her passport, no VOA processing time. Thanks.

Rick

4 hours is very good, no need to worry. just need to present about 45 minutes before the departing time.