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

Here is Why You Need An Adapter

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

Cambodia

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

Type A

Type C

Type G

Nepal

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

Type C

Type D

Type M