The country is very safe to travel despite the fact that it is the poorest countries in the area. However, you should take common sense as you would when travelling anywhere.
Throughout your Lao trip, always keep valuable belongings like passport, air tickets in hotel safe whenever possible. Most of hotels have safe in rooms.
Capital city of Vientiane, you will feel pretty safe walking at night, however the locals here tend to go to bed early so the streets are quite after 9:30pm.
Don’t forget to have some hotels name card in your pocket as to show your taxi drivers if you don’t want to walk back. Besides, wearing expensive jewelry walking at night is unadvisable.