free association vs thought

free association and thought both are nouns.

Word	Noun	Adjective	Verb	Adverb
free association	Yes	No	No	No
thought	Yes	No	No	No

As nouns, thought is a hypernym of free association; that is, thought is a word with a broader meaning than free association:

free association: a thought process in which ideas (words or images) suggest other ideas in a sequence
thought: the process of using your mind to consider something carefully

Other hypernyms of free association include cerebration, intellection, mentation, thinking, thought process.

free association (noun)	thought (noun)
a thought process in which ideas (words or images) suggest other ideas in a sequence	the process of using your mind to consider something carefully
	the content of cognition; the main thing you are thinking about
	the organized beliefs of a period or group or individual
	a personal belief or judgment that is not founded on proof or certainty