Most buses from SIN stop at either Central KL (bukit bintang area), or Bandar Utama. Not sure off hand of any that stop in PJ itself, though I'm sure other forumers will chip in with more info.

Anyway Aeroline has some services that stop at Sunway Pyramid (6km taxi/uber/whatever from Asia Jaya) and One Utama (12km).

Or you could take Starmart to KL Central and hop on to the LRT to Asia Jaya (a couple of stops).

Personally I don't bother with buses though, whenever I go to KL I always just fly. Plenty of low cost carriers going to all three 'airports' i.e. KLIA, KLIA2, Subang.