You Do Need power plug adapter while traveling from Wales 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 Wales is G. This is how they look like.

Wales

In Wales, outlets of type G are in use.

Type G

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