You Do Need power plug adapter while traveling from Hong Kong to Vietnam.

Here is Why You Need An Adapter

The outlet and plug type used in Vietnam are A, B and C and in Hong Kong is G. This is how they look like.

In Hong Kong, outlets of type G are in use.

Type G

In Vietnam, outlets of type A, B and C are in use.

Type A

Type B

Type C

I am from

going to