Are you talking about the bus or the train? I only know about the bus because that's how I did it (plus the bus is faster and runs hourly as opposed to once a day).

In spite of all the hype about Nanning being China's gateway to SE Asia, you wouldn't know it by walking around town; many people here have no clue where Vietnam even is.

In any event, I read somewhere that China is planning on building HSR between Nanning and the VN border (presumably also somewhere in Pingxiang), but the border to Hanoi isn't China's problem.