Spicy jaew bong sauce with kaipen
Type Snack
Place of origin Laos
Region or state Luang Prabang
Main ingredients Green algae, vegetables, sesame seeds
  Media: Kaipen

Kaipen, also Kai Paen (Lao: ໄຄແຜ່ນ) is a Laotian snack made of fresh water green algae, vegetables, and sesame seeds.

Kaipen is produced in the city of Luang Prabang in Northern Central Laos. During the hot dry summer months, when the river level is at its lowest, the green algae, called kai, is gathered from the river bottom. It is washed in the river and then hung to dry. After drying for a day, the kai is pounded and pressed into thin sheets along with vegetables which may include green onions, galangal, garlic and or tomato, and sprinkled with sesame seeds. The finished product resembles a large sheet of Japanese nori.

Kaipen is rich in vitamins and minerals and tastes similar to nori, but is slightly more sweet, bitter, and aromatic. Kai can be eaten by itself or used to flavour other foods. Flash-frying is the preferred method of preparation, after which it can be eaten like a potato chip. Eating fried kaipen while drinking a cold Beerlao would be optimal. Many people in Laos also eat kaipen without prior cooking, although the safety of doing so could be questioned as it is a raw food. In 2007, some markets in the United States began to sell kaipen.

The algae is sometimes identified as Cladophora sp. or Dichotomosiphon tuberosus.