national capital vs Krung Thep

national capital and Krung Thep both are nouns.

Word	Noun	Adjective	Verb	Adverb
national capital	Yes	No	No	No
Krung Thep	Yes	No	No	No

national capital (noun)	Krung Thep (noun)
the capital city of a nation	the capital and largest city and chief port of Thailand; a leading city in southeastern Asia; noted for Buddhist architecture