The vast majority of KLM flights park at a gate, from which arriving passengers emerge into the boarding area - so no problem whatsoever in getting back onto the same aircraft.

Very occasionally KLM flights park on a remote stand (this hasn't happened to me for at least a year, but it does happen). If this happens to you make sure you don't exit into the baggage hall - you need to do a U-turn just before the baggage hall and go up an escalator which will take you back into the departure area.