There might be a way of doing that (the guys on the SQ forum would know better) - it is certainly possible if you were on CX in and out, but you need to go through transit security to the departure level to get to the lounge and then get a special permit to get you back down to the arrivals level to go landisde.

Alternatively, there is a very convenient left luggage facility in the arrivals hall which would also do the job and probably be less hassle. Details here: http://www.hongkongairport.com/eng/tbu/baggage_left.htm
Price HK$55 (about US$7) per piece for the duration you require.