Most hotel check in time is around 12,but you might be able to leave your luggage at the storage area.
You will not be allowed to check in so early.
The only way to check-in that early in the morning is book a room for the night before.
you can check in from 6AM onwards if there is room available (there is digital board showing availability of rooms) check with the staff there, by paying extra RM5/room for early check-in
At First World Hotel, standard check-in time is 3 pm (& check-out time 11 am). If you pay for the room a night before, you can certainly check in at wee morning when you arrive.
Alternatively, you have the option of booking by 3-hourly block as follows.