It depends on what time you arrive in KUL and what time you will depart from KUL. In my experice, if the time between two flight is no more than 12hrs, usually you can do it in Changi.
I have few flight such that I arrive KUL 10om and depart before 12noon next day, they allow me to do that. But if my flight depart after 12noon, then they could not