I'm a AA EXP/Oneworld Emerald.

Despite having done this multiple times in the last couple of months, I was turned away at both the MH First class lounge and CX lounge at KLIA with a SIN-KUL-MYY flight. Agents at both lounges cited that since I was connecting to a domestic flight, I was only entitled to the MH domestic lounge.

I don't think there's anything explicit written about this. Trying to find a oneworld email/contact to seek clarification/escalation. Don't like agents making rules up...

Sigh..