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You will have to pass through immigration to get from KLIA (where Terminal M is) to KLIA2 (the low cost carrier terminal aka LCCT). Furthermore, you will have to take a very short train ride (or taxi ride) to get from KLIA to KLIA2. You will pass through immigration after Terminal M. KLIA and KLIA2 are not connected terminals. They are two separate terminals sharing the same runway and airport code (KUL).
It looks like there is a Sama-sama Express hotel at KLIA2. There also a few hotels near KUL.