You Do Need power plug adapter while traveling from Namibia to Cambodia.

Here is Why You Need An Adapter

The outlet and plug type used in Cambodia are A, C and G and in Namibia are D and M. This is how they look like.

Namibia

In Namibia, outlets of type D and M are in use.

Type D

Type M

Cambodia

In Cambodia, outlets of type A, C and G are in use.

Type A

Type C

Type G