Expecting everything to be blow-your-head-off spicy
Alright, cowboy, we get that you're a tough guy for requesting your food "Thai spicy." But many traditional Thai dishes don't have any heat, like kuai-tiao nam (a clear pork-based broth), kao mun gai (chicken and rice), and, yes, pad Thai (you can add your own chili flakes, but it shouldn't knock you on your ass).
"Thai food is all about balance of flavors -- spicy, sweet, salty, sour, and umami," says Suansilphong. Spice fluctuates regionally, as well. You may have heard that the food of Isaan (Northeast Thailand) is extra spicy, but it's Southern Thailand that has truly ferocious Scoville levels. "To be honest, I think the south can out-eat the north and central on spice levels!" says Lee. So basically, find out if a dish is supposed to be spicy before wilin' out on the chili. And if you do want that spicy dish really spicy, the phrase for extra spicy is "phet mak."