Are you on a short layover ? Closest one to HKIA is at Tsing Yi, also at Mei Fu and CSW so you don't have to go all the way into the heart of Kowloon. Nothing at the Expo or CityGate.

HSBC does have a branch, staffed inside T1 with the usual banker's hours.

https://www.sc.com/hk/atms-and-branches.html