spread to today's Northeast Thailand following the construction of the Northeastern railway line during the turn of the 19th–20th centuries. The dish became more popular after the opening of Mittraphap Road in 1957, helping bring new papaya cultivars into the region, and has since become widely adopted by the ethnic Lao people of both Isan and Laos. Likewise, the hot flavour also spread to Isan and Laos from Central Thailand, which had been introduced to chilli peppers first. However, chilli peppers, like papayas, were already fully integrated in the Lao territory by the time French explorer Henri Mouhot visited Laos, in 1861, and also in the Lao traditional culinary recipes. Furthermore, during the 1950s and 1960s, green papaya salad and other Lao dishes were rarely known in Bangkok and could only be found around the boxing stadium that gathered boxers and fans from Northeastern Thailand, as well as in mobile food carts outside construction sites with workers from Northeastern Thailand and gas stations serving long-distance bus drivers. During the standardization of the Thai national cuisine, green papaya salad was among the Northeastern or Lao dishes to be included into the Thai national cuisine and modified by reducing the amount of chilli peppers and increasing the amount of sugar. Preparation The dish combines the five main basic tastes: sourness of the lime, the spiciness of the chili, saltiness and savoriness of the fish sauce, and sweetness of palm sugar. The ingredients are mixed and pounded in a mortar, which is reflected in the Khmer, Lao and Thai names for the dish that literally mean "pounded papaya". In Laos, green papaya salad is one of the traditional staples of the Lao. Pounded salads in Laos all fall under the parent category of tam som, which may or may not contain green papaya, however, when no specific type of tam som is mentioned, it is generally understood to refer to green papaya salad. For absolute clarity, however, the name tam maak hoong may be used, since this name means "pounded papaya". In Thailand, it is customary that a customer ask the preparer to make the dish suited to his or her tastes. To specifically refer to the original style of papaya salad as prepared in Laos or Isan, it is known as or som tam Lao or simply as tam Lao and the dish as prepared in central Thailand may be referred to