Thai food in Japan (Why does my stomach always hurt more than usual)?

Question:

I have a generally sound stomach and I can easily eat most spicy food without having a problem. Since I moved to Japan I notice that every time I eat Thai food, the next morning is a 1 hour hell in the bathroom.

The weird thing is that I went to Thailand and my stomach was fine for most of the trip. This also never happened in America. It just feels like a normal upset stomach but then when I go to the bathroom my butt is on fire! Is there some spice that they may be using as a substitute for something hard to find in Japan?

Answer:

And someone in Travel Japan is supposed to help you how?? Shameless about your bodily functions are you? Go to the Health section.