There are dozens of varieties of chilies that fall under the category of Thai peppers all of which originate from three species originally found in Thailand. They all share common characteristics, colors, and general heat. You’ll typically get some solid heat and flavor out of any chili labeled as Thai peppers. 
 
There are also lots of products based around Thai chilies, from pepper flakes and hot sauces, to marinades and powders. These are very popular for their hot kick, and the fact that they can add heat in a pinch for Thai dishes if needed.
 
Plants are prolific and are great for containers. Thin-walled, 3 to 6-inch long by 1/2 inch fruits begin green and mature to red.