The places in the South are newly added regions, less than 200 years ago. The only surprise the those Southern Khmer are so completely Vietnamized today, everyone identify themselves as Vietnamese. But now big problem is there is a latent division sentiment at the South.
North and South dont mix. Seldom you see Saigon people in Hanoi and vice versa.
That is the reason I strongly suggest getting China in and build HSR. It will reduce Hanoi Saigon to 4 hour trip, and get people close together.
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