You certainly can't retrieve you luggage and recheck it without going through HK Immigration.

You would need to ask the Singapore Airline experts as to whether they still check bags through. I guess they would if this is all one ticket, and they might if it is two.

You would need to ask China Eatsern about retrieving luggage on your behalf at HKG.

Worst case, 2 hours should be doable to go through HK Immigration and do it yourself assuming you don't need a visa to do that, and no delay on the inbound flight.