It is generally safe to walk in town during the day. Vietnamese people are very curious but friendly. Just be careful when walking out very late (after midnight) in the big cities like Hanoi or Saigon, there might be some kinds of theft in the quiet / empty streets.

Warning: There have been frequent reports of theft at Hanoi's crowded night market. This market happens on the weekend. The usual story sees people having their bags unknowingly slashed and the contents stolen. If you plan on going to the night market do not take a bag of any kind, and only take what money you will need. Leave your passport in your hotel safe. 

See also other FAQs

Do the night clubs and bars open late at night?