At KLIA
Dawn departures, and arrivals after the last Ekspres. You can still train in for the daylight.
Confirm you are booking the main terminal or klia2. They are not the same building.
KUL · Where to sleep · published · checked
Where to sleep on a Kuala Lumpur layover
The express train is good enough that a city hotel is right, except when the flight leaves before the first one. Then sleep at the airport.
KL Sentral
The layover base. You walk to the train that goes to the aircraft, and you change once for KLCC.
It is a station, not a village. Ask for a quiet room.
KLCC
The right upgrade on 48 or 72 hours if the towers are the point. Check the last hop from KL Sentral on a map before you book. One LRT or a short Grab is fine. A tour of the ring road is not.