The Muay Thai hook kick -- also called the spinning hook kick or reverse roundhouse -- is one of the most devastating techniques in a fighter's arsenal. When it lands clean, fights end. Period.
Here's the thing. This is an advanced technique. You should NOT be throwing hook kicks until your side kick and back kick are solid. Those are the foundation kicks that build the hip rotation and balance you need for the hook kick to work.
The basic mechanics start with a spin. From your fighting stance, you pivot on your lead foot and rotate your body away from your opponent. As you come around, your rear leg whips in a hooking arc toward the target -- usually the head.
The striking surface is the heel. Not the instep like a roundhouse. The heel carries more concentrated force, and the whipping motion at the end of the spin generates tremendous power.
The biggest mistake people make is spinning too wide. The kick should be tight and compact. Think of your leg as a whip -- the tighter the arc, the faster the snap at the end. If you're swinging your leg in a big wide circle, you're telegraphing it and you're slow.
Timing is everything with this kick. You don't throw it from neutral. You throw it after your opponent commits to something -- after a jab, during a combination, when their hands are occupied. The spin takes you offline, and the kick comes from an angle they're not defending.
One more thing. Your eyes need to find the target as early as possible during the spin. The faster you spot your opponent, the more accurate the kick. Spinning blind is how you miss and end up off-balance with your back turned.
For a complete breakdown of every kick type, check out our full guide to types of kicks in martial arts. Get the full course in the Ultimate Muay Thai Training System.