Loi means "to float" and krathong is a "leaf cup" or "bowl." On the evening of the festival, Thais gather at the water after sunset to launch small lotus-shaped banana leaf or paper boats, each of which holds a lighted candle, a flower, and a small coin to honor the water spirits. Some say that the krathong is also a tribute to the snake named Phrajanag who lives at the bottom of the river or canal. According to legend, Phrajanag literally followed in the Buddha's footsteps and succeeded in reaching Nirvana.
Krathong or leaf cups, usually in the shape of a boat or a bird, go on sale several days before the festival. These commercially made krathong are really more like toys, and the stalls selling them are confined largely to cities and towns. In rural areas, people still make their own by hand.
The individual who has set the krathong afloat makes a wish as it drifts out of sight. If the candle is still burning when it disappears from view, it is believed that the wish will come true.
The paper or banana-leaf krathong are both an offering to appease the spirits of the river and a way of freeing oneself of the sins of the preceding year.