You Do Need power plug adapter while traveling from South Sudan to Vietnam.

Here is Why You Need An Adapter

The outlet and plug type used in Vietnam are A, B and C and in South Sudan are C and D. This is how they look like.

South Sudan

In South Sudan, outlets of type C and D are in use.

Type C

Type D

Vietnam

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

Type A

Type B

Type C