West Malaysia vs Malaya

West Malaysia and Malaya both are nouns.

Word	Noun	Adjective	Verb	Adverb
West Malaysia	Yes	No	No	No
Malaya	Yes	No	No	No

As nouns, West Malaysia and Malaya are synonyms defined as:

West Malaysia and Malaya: the region of Malaysia on the Malay Peninsula; shares a land border with Thailand to the north

Other synonyms of West Malaysia include Peninsular Malaysia.

West Malaysia (noun)	Malaya (noun)
the region of Malaysia on the Malay Peninsula; shares a land border with Thailand to the north	the region of Malaysia on the Malay Peninsula; shares a land border with Thailand to the north