I'm traveling from Macao to India with Air Asia and have an 8-hour transit in Kuala Lumpur.
I do not plan to leave the airport, but I'm wondering if I need a transit visa for Malaysia.
Looking at the original verbiage of your question, if you are using AirAsia's Fly-Thru service, then you can remain airside and not enter the country.
If you are not using the Fly-Thru service, then you will need to enter the country, claim your checked bags and then check in for the second flight, as AirAsia is primarily a point to point carrier (except fares with Fly-Thru). What visa may be required in this case is solely dependent on your nationality, which we don't know at the moment.