Yes, THINKS is a Scrabble word!

Letter values in Scrabble US: T 1, H 4, I 1, N 1, K 5, S 1.

Is it a valid word?

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

judge or regard; look upon; judge
expect, believe, or suppose
use or exercise the mind or one's power of reason in order to make inferences, decisions, or arrive at a solution or judgments
recall knowledge from memory; have a recollection
imagine or visualize
focus one's attention on a certain state
have in mind as a purpose
decide by pondering, reasoning, or reflecting
ponder; reflect on, or reason about
dispose the mind in a certain way
have or formulate in the mind
be capable of conscious thought
bring into a given condition by mental preoccupation

Also: call back, call up.