Siamese vs Siam

Siamese and Siam both are nouns.

Word	Noun	Adjective	Verb	Adverb
Siamese	Yes	Yes	No	No
Siam	Yes	No	No	No

Siamese (noun)	Siam (noun)
a slender short-haired blue-eyed breed of cat having a pale coat with dark ears paws face and tail tip	a country of southeastern Asia that extends southward along the Isthmus of Kra to the Malay Peninsula
a branch of the Tai languages, spoken in central Thailand, centered in Bangkok
a native or inhabitant of Thailand

Siamese (adjective)	Siam (adjective)
of or relating to Thailand
of or relating to the languages of the Thai people
of or relating to or characteristic of Thailand or its people