Throws are a good thing in Muay Thai. If you've ever been dropped on your ass several times during a fight it does a couple of things:
1. Demoralizes You. Makes you feel like a little bitch being thrown down to the ground.
2. Tires you out. Being dropped on your ass several times and having to lift it off the mat sux
3. Demonstrates to the judges that you control your opponent.
Throws are typically done while in the clinch and you can't trip with your feet. The most common throw is from the clinch, opponent knees, you twist your upper body (while pushing and pulling with your hands) towards the side of the leg planted on the ground. There are some other really cool throws; grabbing the knee with your hand and lifting, bending your opponent backwards, using your knee to lift your opponents knee higher and tossing, etc.
Check out the fight between Buakaw vs. Takayuki Kohiruimaki in K1 Max 08Jul04.
Buakaw v. Takayuki
Buakaw puts on a clinic on the Muay Thai throw. It's a good technique and is hard to learn. I spent a week in Thailand trying to learn that one technique. I got dropped on my ass so much that my butt and ego were bruised.
Joe