Yes, KHAT is a Scrabble word!

Letter values in Scrabble US: K 5, H 4, A 1, T 1.

Is it a valid word?

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

the leaves of the shrub Catha edulis which are chewed like tobacco or used to make tea; has the effect of a euphoric stimulant

Also: arabian tea, african tea.

Not playable in Scrabble US: QUAT.