I'm planning on BKK-SIN, SIN-NRT flights on two separate PNRs.
BKK-SIN wouldn't be on *A (either on Jetstar or Air Asia ).
I'll fly BKK-SIN a day before my SIN-NRT flight and would like to leave the airport for dinner and come back.

Will I be able to check-in for SIN-NRT 24 hours before at BKK airport?
I'd rather not spend money on hotel this time, and use SKL sleeping room instead.