You Do Need power plug adapter while traveling from East Timor (Timor-Leste) to Cocos (Keeling) Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Cocos (Keeling) Islands is I and in East Timor (Timor-Leste) are C, E, F and I. This is how they look like.

East Timor (Timor-Leste)

In East Timor (Timor-Leste), outlets of type C, E, F and I are in use.

Type C

Type E

Type F

Type I

Cocos (Keeling) Islands

In Cocos (Keeling) Islands, outlets of type I are in use.

Type I