Is he ticketed on LAX-KUL? If that is the case, then no, mileage will not be earned or posted until he completes the trip to KUL.
If he is ticketed on separate LAX-TPE, and TPE-KUL segments, then there is a chance the system will post the miles of the first segment to his account by the time he lands in TPE. But I wouldn't count on it either.