Originally Posted by
UAPremExecflyer
No ... unless you have your BP stamped by the check-in agent ... the initial security check will not let you go to immigration check and airside (transit area) without a same-day BP
Really? I didn't realise that.
Maybe I misunderstood the OP, but I think they would be allowed airside as long as they have a valid boarding pass. For SQ, you can check in 48 hours before hand, so I believe you should be able to get airside at that time. I've also read trip reports elsewhere where travellers go to the Private Room the night before and then go sleep in the transit hotel (why?!) and then return to the Private Room the next morning.