thoughtful vs paying attention

thoughtful is not a noun while paying attention is a noun.

Word	Noun	Adjective	Verb	Adverb
thoughtful	No	Yes	No	No
paying attention	Yes	Yes	No	No

As adjectives, thoughtful and paying attention are synonyms defined as:

thoughtful and paying attention: taking heed; giving close and thoughtful attention

Other synonyms of thoughtful include attentive, heedful.

thoughtful (noun)	paying attention (noun)
	paying particular notice (as to children or helpless people)

thoughtful (adjective)	paying attention (adjective)
exhibiting or characterized by careful thought	taking heed; giving close and thoughtful attention
taking heed; giving close and thoughtful attention
considerate of the feelings or well-being of others
having intellectual depth
characterized by solemn, sincere manner