@Khongcanhoi,
Friends who have visiting the larger cities in Vietnam all advise to view youtube videos on the dos and don'ts of walking along and crossing streets in the heavy moto traffic. There is a fine art and skill to it that they describe as much like the video game frogger where you are leaping between motos, bikes and other vehicle types. There are no official lanes but the traffic is usually 6 lanes deep and doesn't stop for anything.
Think of it as being akin to traffic I've experienced in Boston, Mass, only a lot more vehicles and more chaotic.