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

Here is Why You Need An Adapter

The outlet and plug type used in Cambodia are A, C and G and in Costa Rica are A and B. This is how they look like.

Costa Rica

In Costa Rica, outlets of type A and B are in use.

Type A

Type B

Cambodia

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

Type A

Type C

Type G