I'm an US passport holder, and frequent travel with a non US Passport holder. There are SOME airports that he has to have what is called a transfer visa (he doesn't pass thru immigration either) to be allowed to board flight to connecting city. As each city in the world is different for each nationality, I would contact a Malaysian Embassy to ask for sure. You won't get very far at checkin if you say well some guy on Flyertalk told me I didn't need one.