Yes, CHASSIS is a Scrabble word!

Letter values in Scrabble US: C 3, H 4, A 1, S 1, S 1, I 1, S 1.

Is it a valid word?

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

alternative names for the body of a human being
a metal mounting for the circuit components of an electronic device
the skeleton of a motor vehicle consisting of a steel frame supported on springs that holds the body and motor

Also: human body, physical body, material body.