Teep; thrust kick. It's a straight kick done by cocking your leg up and thrusting it forward hitting with the ball of your feet.
Defense? Same technique to his other leg. This is one of those basic techniques that is really good because it is indeed like the jab. Not much you can do about them beside proper footwork.
Use circular movements around your opponent. If you notice, the most dominant thai boxers always occupy the center of the ring. Why? He's not strategically at an advantage. He's just slow. To align the teep properly, you sacrifice some co-ordination and balance. Imagine if your target was always going to your sides, never standing infront of you.
Use good footwork.
This is an orthodox technique I use, but I'm not sure it would work for you. As he is about to perform the teep, move right into his line of attack. If he hasn't been able to fully extend his leg, he will fall backwards. Sometimes, just walk into his line of attack before he manages to completely extend his leg and land a nice clean hook on him with your right hand.
Or you could just try and parry it like most good karate-kas. Never seen it work though.
Or as a judo-man (ME!) step slightly to the side, grab something, and go for the clinch. Don't worry if you get hit, we are hittable unlike those sissy Muay Thai guys. We love to get hit, and we are so good at it, we don't hit back. However, the floor wants to get to know you real badly :P
I got two fists.. Don't make me use my head as well!