You Do Need power plug adapter while traveling from Isle of Man to Vietnam.

Here is Why You Need An Adapter

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

Isle of Man

In Isle of Man, outlets of type C and G are in use.

Type C

Type G

Vietnam

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

Type A

Type B

Type C