In their website, Singapore Airlines write about online check-in (at https://www.singaporeair.com/en_UK/au/travel-info/check-in/online-mobile-checkin/). It is mentioned:
At the airport, proceed directly to the Immigration counter if you don’t have bags to check in and if you don’t require travel document/visa/credit card verification at the check-in counter.
It is sometimes quite important to know whether you have to go to the check-in counter because if you arrived from another flight that is on a separate ticket, this would mean you have to go through immigration and then go back airside (rather than just staying airside the whole time).
Does anyone know in what cases such "travel document/visa/credit card verification" is required?
Also, I assume if it is required when are you notified of this, in advance (via e-mail e.g.) or when you do online check-in?
Thank you very much.