Yes, FOLKSONG is a Scrabble word!

Letter values in Scrabble US: F 4, O 1, L 1, K 5, S 1, O 1, N 1, G 2.

Is it a valid word?

FOLKSONG is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

a song that is traditionally sung by the common people of a region and forms part of their culture

Also: folk song, folk ballad.