Yes, LAS is a Scrabble word!

Letter values in Scrabble US: L 1, A 1, S 1.

Is it a valid word?

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

a white soft metallic element that tarnishes readily; occurs in rare earth minerals and is usually classified as a rare earth
a state in southern United States on the Gulf of Mexico; one of the Confederate states during the American Civil War
the syllable naming the sixth (submediant) note of a major or minor scale in solmization

Also: atomic number 57, pelican state.

Not playable in Scrabble US: LOUISIANA, LAH.