Thailand vs Kingdom of Thailand

Thailand and Kingdom of Thailand both are nouns.

Word	Noun	Adjective	Verb	Adverb
Thailand	Yes	No	No	No
Kingdom of Thailand	Yes	No	No	No

As nouns, Thailand and Kingdom of Thailand are synonyms defined as:

Thailand and Kingdom of Thailand: a country of southeastern Asia that extends southward along the Isthmus of Kra to the Malay Peninsula

Other synonyms of Thailand include Siam.

Thailand (noun)	Kingdom of Thailand (noun)
a country of southeastern Asia that extends southward along the Isthmus of Kra to the Malay Peninsula	a country of southeastern Asia that extends southward along the Isthmus of Kra to the Malay Peninsula