Question: Karma applies only in this realm – only in this material world, right? Or does it also apply to the soul in the non material world?
Karma is cause and effect as a result of work.
We exist on one side of the kāraṇa ocean (the ocean of causality). Ours is the side where a lack in the soul motivates work (karma) which sets cause and effect in motion. The other side of the ocean of causality, the “non-material realm” or the “spiritual world” as we often call it, is “Vaikuṇṭha” – a place where there is no want whatsoever. On that side of existence it is not a lack in the soul but the fullness of the soul which motivates action. Thus the action is not “work” (karma) but “play” (līlā).
Play also has sequence to it, and thus follows a type of cause and effect – but the whole thing is effortless and free, so it is not called karma, it is called līlā.
Vraja Kishor das