You Do Need power plug adapter while traveling from Cocos (Keeling) Islands to Hong Kong.

Here is Why You Need An Adapter

The outlet and plug type used in Hong Kong is G and in Cocos (Keeling) Islands is I. This is how they look like.

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

Type I

In Hong Kong, outlets of type G are in use.

Type G

I am from

going to