Incorporeal beings ignoring normal armor and shields. But the ring of force shield provides a force effect. Does that work, as force-effects work on incorporeals?
Yes, it does
Ring of Force shield states:
The Wall of Force Spell has the [force] keyword
Incorporeal Creatures say:
Since the Ring duplicates a spell with the [force] keyword, it is a force effect and thus would work normally against incorporeal creatures.