Last year, I was in and out of SGN without any problem with a Thai passport. I've never been harassed at any other airports in asia either (ICN, BKK, HKG, SIN, DLC, YNT, KUL).

I usually travel alone; either as college student or young professional. Sometimes, I will have a colleague (usually asian) accompanying me on business trips.

So, I am not sure why your friend get harassed. If anything, I would think I would be an easy target.

rgds,
Drew