if dep flight is 0655am from HKIA,pls adv time to wait for the bus & where to buy ticket. We at Casa Hotel

You need to go to the Public Square Street, Nathan Road Station on Nathan Road near your hotel to take bus line N21.

The bus N21 operates from 01:30 to 05:10 with interval around 20 minutes from Tsim Sha Tsui area. You need to reach the airport at least about two hours in advance, so you may need to wait for the bus at around 03:00 or earlier.