Vietnam is one of the safest countries for traveling. However, you should take great care with your personal possessions, especially when you are in big cities such as Ho Chi Minh city, Nha Trang or Hanoi, where there has been an increase in bag snatches.
Leave all your valuables, documents, credit cards, etc. at hotel, at the reception desk before venturing out at any time. There are safety boxes at every hotel. But you should register your valuable possessions at front desk. Check with hotel front desk when you check in.