Lao food centers on sticky rice, fresh herbs, and fermented fish sauce (padaek), and it is eaten with your hands — a small ball of sticky rice doubles as your spoon. Vientiane and Vang Vieng both have street stalls, markets, and riverside restaurants serving the same dishes locals eat, so you do not need to look for a separate "tourist" menu.
What to try
Laap (also spelled larb) is Laos' national dish: minced meat — chicken, pork, beef, or duck — tossed with lime juice, fish sauce, mint, toasted rice powder, and chili, eaten with sticky rice. Tam mak hoong, green papaya salad pounded with chili, lime, and padaek, is spicier and more pungent than the Thai version most travelers already know. Khao piak sen, a chicken or pork noodle soup with thick rice noodles, is the standard breakfast. Sticky rice (khao niew) comes in a small woven basket with almost every meal.
Skip the raw version
Laap and a few other dishes are sometimes served "dip" — raw or barely seared meat or fish instead of cooked. Raw freshwater fish carries a real risk of liver fluke (Opisthorchis viverrini), a parasite that is a documented public health problem in Laos and is linked to liver disease after repeated exposure over years. Squeezing lime over the dish or washing it down with alcohol does not kill the parasite, despite that being a common local belief. Ordering the cooked version — usually just called laap or laap sin — gets you the same dish without the risk.
Street food safety
Street food in Vientiane and Vang Vieng is generally safe if you follow the same habit locals do: eat where the stall is busy and the food is cooked in front of you rather than sitting out. Stick to bottled or boiled water, skip ice you cannot vouch for, and wash or sanitize your hands before eating, since most meals are eaten by hand.
Where to find it
Markets are the easiest starting point — Vientiane's morning market and the riverside night market both have food sections where you can see a dish before ordering it. Stalls aimed at travelers often have photo menus, which help if you do not speak Lao.