Vut Kamnark's instructionals are really well thought out. He's got a degree in sports science/kinesiology as well. He's able to effectively say what many Thai trainers can't because of poor language/communication skills. He's in part responsible for the art of Muay Thai gaining popularity in the US in the 90s. And yes his low kick is a whole different animal compared to the Calsanz guy. The Calsanz guy kicking often leads with his head and thus would get countered to bits. He's also desperately trying to push his kick as opposed to give it that whip like action that you see in Vut's instructional. I'm not sure how old he is when he made these instructionals because they've been out for a long time. But needless to say he's not exactly young in these vids and he's in great shape with a proper fighters physique.