Banana stalk krathong are also biodegradable, but styrofoam krathongs are sometimes banned, as they pollute the rivers and may take years to decompose. A krathong is decorated with elaborately-folded banana leaves, incense sticks, and a candle. A small coin is sometimes included as an offering to the river spirits.
On the night of the full moon, Thais launch their krathong on a river, canal or a pond, making a wish as they do so. The festival may originate from an ancient ritual paying respect to the water spirits.