Khao piak sen
Although the words literally translate to "wet rice strands," this soup is significantly more appetizing than its name implies. The thick round noodles are made from a mix of rice and tapioca flour, which gives them a delightfully chewy texture and usually leaves the broth they're cooked in slightly viscous, too. Meat toppings vary but can range from chopped chicken to fried pork and blood cakes, and bowls come topped with a spoonful of fried garlic. You'll know which vendors have khao piak sen because the noodles, which come in different widths, are dusted with white flour.
Often sold alongside khao piak sen, khao pun is made with thin fresh rice noodles, similar to vermicelli or khanom jeen. They come in a clear broth flavored with herbs, fishballs and unidentifiable pork parts. Toppings include roughly chopped strands of lean pork, sausage slices and offal, and khao pun is always served with a separate platter of raw vegetables and herbs—less to add to the soup itself and more to snack on between slurps.
Khao pun nam phik
Another variation on khao pun, made with a rich, spicy coconut milk-infused broth and minced pork. Coconut milk doesn't play a huge role in Lao cuisine, but this laksa-like dish seems to have taken root, though it's admittedly a little harder to find than khao pun and khao piak sen. Look for vendors who have a big tray of chopped banana flowers, long beans, cabbage and herbs, which are all added to the bowl before serving.
Pronounced "fer," this hugely popular dish is, perhaps unsurprisingly, similar to the famed Vietnamese soup, but made with a different grab bag of spices and herbs flavoring the broth. Other common ingredients include fish balls, pork balls, Vietnamese sausage and sliced pork, and, in this case, crispy puffed rice cakes that we were instructed to crumble over the soup. Like khao pun, pho is served with a separate plate of raw vegetables and herbs to munch on. Some pho vendors also distribute little bowls of homemade peanut sauce to dip the raw veggies into.
Not to be confused with the Northern Thai curry soup of the same name, Lao khao soi (which is usually sold alongside pho) is almost like Bolognese soup. Flat rice noodles are topped with a hearty sauce of minced pork, tomatoes, peanuts, and chilils, then thinned out with a splash of pho broth and served with yet more fresh raw green things. Why this soup has the same name as a Thai dish to which it does not in any way resemble remains a mystery to me.
UPDATE I: Pok Pok owner and Thai food evangelist Andy Ricker helped me better understand the confusing nomenclature of khao soi vs. khao soi: "Khao soi means 'cut rice' and refers to the noodles used, so although it is the name of a dish, different dishes can have the same name. Long ago, Northern Thai khao soi probably was made from cut rice noodles too, even though now it is made with wheat noodles. To confuse matters, and you'd need to speak to a linguist and a food historian about this, a long time ago when wheat was introduced, they had no reference for it except rice. So wheat is called Khao Salee (Khao means rice), or a different form of rice so perhaps they were referring to wheat noodles."
UPDATE II: Andy then referred me to Thailand-based author/photographer Austin Bush who has written guidebooks all over Southeast Asia. Austin says: "With all respect to my buddy Andy—I think he's incorrect about the "cut rice" theory. Yes, translated directly, the Thai words "khao soi" do literally translate as "cut rice", but I suspect that this is simply a coincidence. More likely, the word is the Thai pronunciation of the Burmese hkauk hswe (or khauk hswe or kauk swe) which is their general term for noodles...my guess is that, again, since khao soi probably comes from a word that means simply noodles in Burmese, it has come to be attached to a few different noodle dishes. Incidentally, it's not only available in Laos, and I've encountered it in Myanmar and northern Thailand." So the mystery remains!
Khao piak khao
Laotian rice porridge, which should be familiar to anyone who's experienced Chinese congee or Thai jok. This version, with chopped chicken, fried shallots and scallions, didn't look like much from the outside, until I dipped my spoon in and discovered a barely cooked egg just waiting to be popped beneath the surface. Like most rice porridges, the soup itself is fairly bland, but this is where the table full of DIY condiments really livens things up.
Not technically a noodle soup, clearly, but I'm including it because some of the pho vendors in town also steam up fresh Vietnamese-style rice flour rolls (aka banh cuon). This one is called nam khao sai kai, and it's basically a giant banh cuon roll on steroids. Lurking inside of that slippery, neatly folded package is a mix of minced pork and mushrooms, plus a runny steamed egg that's been grafted to the rice flour.