The words “tom yam” are derived from two Thai words. Tom refers to the boiling process, while yam refers to a Thai spicy and sour salad. Tom yum is characterised by its distinct hot and sour flavours, with fragrant spices and herbs generously used in the broth. The soup is also made with fresh ingredients such as lemongrass, kaffir lime leaves, galangal, lime juice, fish sauce, and crushed red chili peppers.

Commercial tom yum paste is made by crushing all the herb ingredients and stir frying in oil. Seasoning and other preservative ingredients are then added. The paste is bottled or packaged and sold around the world. Tom yum flavored with the paste may have different characteristics from that made with fresh herb ingredients. The soup often includes meats such as chicken, beef, pork, or shrimp.