Does som tam taste the same everywhere?
No. The chilies, the seasonings and the way sweetness is added differ. If the fermented aroma is unfamiliar, it helps to ask first whether plara is used.
Som Tam · ส้มตำ
If you want something crunchy and tangy, try som tam. It is a salad of shredded unripe papaya pounded in a mortar with seasonings. The papaya takes on sour and spicy flavors and goes well with sticky rice or grilled food. In Isan some versions use a fermented fish seasoning, so if the fermented aroma is unfamiliar, ask what kind of som tam it is when you order.

The crunch of papaya meets a sour, spicy dressing. In versions that use plara, a fermented fish seasoning, you can also notice a fermented aroma. Even with the same som tam, the taste changes with the way the seasonings and chilies are used.
If you want less heat, say so before it is made.
Som tam is Isan's signature dish and is eaten in many Thai cities. Even within Isan there are different kinds from place to place, so you can compare the taste of som tam from one town to another. On a trip to Khon Kaen, try it with sticky rice and other Isan dishes.
No. The chilies, the seasonings and the way sweetness is added differ. If the fermented aroma is unfamiliar, it helps to ask first whether plara is used.
Not necessarily. Some kinds use fish seasoning or shrimp. If you are vegetarian, ask whether the dressing and the toppings are suitable as well as the papaya.
If you want to read more about the food and the regions behind it, these sources are a good next step. Ingredients and cooking methods can differ from one place to the next.
Sharing image credit: Vyacheslav Argenberg · CC BY 4.0