You Do Need power plug adapter while traveling from Vietnam to Myanmar (Burma).

Here is Why You Need An Adapter

The outlet and plug type used in Myanmar (Burma) are A, C, D, G and I and in Vietnam are A, B and C. This is how they look like.

Vietnam

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

Type A

Type B

Type C

Myanmar (Burma)

In Myanmar (Burma), outlets of type A, C, D, G and I are in use.

Type A

Type C

Type D

Type G

Type I