What not to do in Vietnam: When crossing a road heavy with traffic, dont stop or hesitate, keep moving, the traffic (mostly bikes) will flow around you.
-@mikeymac
...and raise your hand, periscope style, waving it at a height above the helmets of oncoming bikes. This way bikes behind them will see that you are there.
I'm glad you brought this matter up, mikeymac. It really is a matter of utmost importance/safety.