Yes, REMISE is a Scrabble word!

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

Is it a valid word?

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

an expensive or high-class hackney
a small building for housing coaches and carriages and other vehicles
(fencing) a second thrust made on the same lunge (as when your opponent fails to riposte)

Also: coach house, carriage house.