hello my wife and I are having a 7 hour stop shower at hong kong international airport.

Yes, for transit passengers, there are Plaza Premium Lounge providing the shower facilities.

The lounge is located at folowing sites.
Level 7, Departures West Hall, Terminal 1 (Near Gate 60);
Level 3, Ground Transportation Centre (Near Airport Express Station (To City) or Coach Station, Terminal 2)
Level 7, Departures West Hall (near Gate 35), Terminal 1
Level 6, Departures East Hall (near Gate 1), Terminal 1. The

Have a try.

hello thank you for the information do we need to pre book the lounges or is it first come first served?

No, you do not need to prebook for it. Just like you said, it is first come first served. In fact, it is in service in 24 hours, and you can find a room or seat available upon your arrival, Don’t worry about it.

thank you very much for helping