Food in Thailand is customarily HOT, spicy HOT. Most Westerners cannot handle the level of spice that Thai people enjoy. To help you order a tasty and pleasurable meal, I would advise any visiting Westerner to use one of the following two phrases (based upon your preference):
Building your tolerance to the Thai spicy levels helps immensely to enjoy the food here. Fortunately I am now able to eat at the Thai level of spice but it did take as much as a year (and I do recommend a slow build up). In fact I would now put myself in the upper percentile for being able to handle the spiciness. Believe me, my body still reacts to the chilis, initially with hiccups to the first few bits then after I get used to the spiciness my nose starts to run, and will continue to run through the rest of meal. Why do I do it you might ask? Well I have found that the chili enhances the other flavors and I now fully understand why the Thai people eat spice at that level.
Tips for the savvy traveler to prepare for the best trip in their lives.