The problem with this thesis is that most asians cannot reliably discern the home of origin of other asians without hearing them speak their native tongue or noticing their dress. (In the same way, a caucasian can't reliably discern that another person is French or German without a clue.)

If one asian sees another all he knows is he sees another asian - and, in fact, even they sometimes make the bigger mistake of not being able to distinguish some south americans from asians.