Yes, MASERS is a Scrabble word!

Letter values in Scrabble US: M 3, A 1, S 1, E 1, R 1, S 1.

Is it a valid word?

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

an acronym for microwave amplification by stimulated emission of radiation; an amplifier that works on the same principle as a laser and emits coherent microwave radiation