paying attention vs thoughtful

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

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

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

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

Other synonyms of paying attention include attentive, heedful.

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

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