The cheapest way may be to take bus S1 from Passenger Terminal Building, Cheong Tat Road of the airport to Tung Chung Station. Then take MTR from Tung Chung station to Lai King. Transfer to Tsuen Wan Line and get off at Tsim Sha Tsui Station. Get out the station from B2 and walk to the hotel. It costs about HKD19.
You can also take bus A21 from Airport (Ground Transportation Centre) to Granville Road, Chatham Road South. Then walk to the hotel. The fee is HKD33.
Well, I think A21 is a better option which is much convenient if you have luggage and kids or it is your first time to HK.