Less well-known outside Thailand is tom khlong (ต้มโคล้ง), a spicy sour soup where the sourness, however, does not derive from lime juice but through the use of tamarind.[12] Tom som (Thai: ต้มส้ม) are soups that are also very similar to tom yum but most often do not contain lemongrass or kaffir lime leaves. Depending on the type of tom som, the acidity can be derived from lime juice or from the use of tamarind.