Because the Tom yum Kung is spicy and sour foods that are primarily made to eat and not greasy, the Tom yum Kung is a popular food in all Thai. Including foreigners will stick out the delicious Tom yum shrimp as well.
Because the food is sour shrimp soup. And spicy essentially Make eating was not greasy Therefore Shrimp is the food that is popular in all over the country. Including foreigners would be attracted to the taste of shrimp soup as well.