shuttle buses from macau airport available 24/7 ? what's the easiest way to get to hou kong hotel?

No, the free buses are not available around the clock. Except taxi, you can take city bus no. 26, which operates till around 23:30, to Rua das Lorchas and walk there. Or take line AP1 to the Border Gate with the fare of 4.2MOP and it operates till around 01:20. Then transfer to the free bus of Sofitel Hotel to the terminal and walk to your hotel within 5min.