No, there is no on-arrival access. When you clear customs and get your hold bag, you won't be able to re-enter the KLIA terminal airside where the lounge is. You'll need to make your way to KLIA2 – a separate terminal on the other side of the airfield – and check-in for AirAsiaX there.
You may want to access a pay-per-use lounge landside at KLIA2 which should be open from 4am.
You may want to access a pay-per-use lounge landside at KLIA2 which should be open from 4am.