living thing vs being

living thing and being both are nouns.

Word	Noun	Adjective	Verb	Adverb
living thing	Yes	No	No	No
being	Yes	No	No	No

As nouns, being is a hyponym of living thing; that is, being is a word with a more specific, narrower meaning than living thing:

living thing: a living (or once living) entity
being: a living thing that has (or can develop) the ability to act or function independently

Other hyponyms of living thing include organism, life, biont, cell.

living thing (noun)	being (noun)
a living (or once living) entity	a living thing that has (or can develop) the ability to act or function independently
	the state or fact of existing