What is the cheapest ride to Wing Sing Hotel from Hong Kong International Airport?

I suggest you to take the bus A21 from the airport and get off at Man Ming Lane, Nathan Road. Then walk about 200 meters to the destination.

The bus fare is HKD 33 per adult, and the kids between 3 and 11 can enjoy the half price.

If you really want the cheapest way, you need to transfer from the MTR to the bus.
You can take the bus E21 from the airport and get off at Sai Yeung Choi Street South. Then walk to the Mong Kok Station to take the MTR Kwun Tong Line and get off at Yau Ma Tei Station. Then walk to the hotel.
The transportation fare is KHD 18.2 in total per person.