Nan River vs Nan

Nan River and Nan both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nan River	Yes	No	No	No
Nan	Yes	No	No	No

As nouns, Nan River and Nan are synonyms defined as:

Nan River and Nan: a river of western Thailand flowing southward to join the Ping River to form the Chao Phraya

Nan River (noun)	Nan (noun)
a river of western Thailand flowing southward to join the Ping River to form the Chao Phraya	a river of western Thailand flowing southward to join the Ping River to form the Chao Phraya