There are heaps of good things to eat in Thailand. But if there was one dish that I would recommend to visitors, particularly because so few foreigners seem to be familiar with it, I would choose khao khluk kapi. This literally means 'rice mixed with shrimp paste', which is a poor description of this vibrant dish that seems to include every favourable flavour and texture in Thai cooking.
The dish is based around rice that has been fried, or sometimes boiled, with shrimp paste, giving it a pleasant fishy odour and a greyish-brown hue. This rice is topped with ingredients that usually include shredded green mango, slices of cucumber, a thin omelet that that has been sliced into strips, thinly sliced shallots, thinly sliced green beans, crispy deep-fried dried shrimp, and sometimes a few slices of kun chiang, Chinese-style pork sausage, and small slices of pineapple. There's always a side of muu waan, pork belly that has been braised in palm sugar and fish sauce, a garnish of few dried chilies deep-fried until crispy, and often a slice of lime. The dish is often, but not always served with a dish of clear broth.
The dish is salty from the shrimp paste, fresh and crispy from the veggies, sweet from the fruit and muu waan, and can also be spicy, if you decide to mix in the chilies. I like to mix everything together beforehand to ensure that I get a bit of each flavour/texture in each mouthful.
For more in-your-face khao khluk kapi action, check out the excellent version done at Ratana; an acceptable take at a local noodle stall; a decent but scant version at Tha Chang market; an improvised version at the Suan Lum Night Bazaar; and a haphazard dish at a local restaurant.