how to go to HK airport from Ngong Ping

You mean you want to reach the Monastery first from your hotel and then head for the airport for your flight, right?
If so, you cannot take the airport express, because it is expensive and this line does not reach Tung Chung.

From where you are, you can walk to the Wan Chai Station to take the Island Line to Central Station. Then walk to the HK Station where you can find the Tung Chung Line to Tung Chung directly. There you can take the Nong Ping 360 Cable car to get to Tung Chung and walk to the Monastery easily. After visiting, you can use the cable car or local public bus line 23 to Tung Chung Station and change to bus S1 to reach the airport directly.

Hope it is useful for you and have a nice trip there ~

Thanks you for your reply. From Tung Chung station to airport, it takes about 40 minutes or more ? This is the first time to go to the Monastery. Therefore, I can't estimate the time for my trip :). I am worry about my flight on 4:20 pm .