Yes, PAJAMAS is a Scrabble word!

Letter values in Scrabble US: P 3, A 1, J 8, A 1, M 3, A 1, S 1.

Is it a valid word?

PAJAMAS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a pair of loose trousers tied by a drawstring around the waist; worn by men and women in some Asian countries
(usually plural) loose-fitting nightclothes worn for sleeping or lounging; have a jacket top and trousers

Also: pj's.