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

Here is Why You Need An Adapter

The outlet and plug type used in Namibia are D and M and in Lesotho is M. This is how they look like.

Lesotho

In Lesotho, outlets of type M are in use.

Type M

Namibia

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

Type D

Type M