Michel Qissi was a technical advisor/choreographer when he overheard the production crew say they were looking for a tall oriental-looking guy with a background in Muay Thai. He volunteered, and got the part of Tong Po.
The title held by Dennis Alexio's character in the movie - the International Sport Karate Association (ISKA) Heavyweight Championship - is a real championship and has been held by Alexio during his fighting career. The belt in the movie, however, is not modeled after the actual belt.
When Kurt gets drunk at the bar with Xien and starts fighting, one of the men breaks a glass bottle in half over the counter and is holding the half bottle. The camera shows Kurt, then goes back to the man and he doesn't have the half bottle in his hand. Then he gets a roundhouse kick to the face.
What are the differences between the R-Rated Version and the German Version?
A
The German Version of Kickboxer is slightly longer because it's based on an earlier cut of the movie before it was released in the States. On the other hand the German Version has been censored for rating reasons and therefore some fight scenes have been shortened. A detailed comparison between both versions with pictures can be found here.