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.