This festival begins immediately after the last day of Lent, and lasts until the next full moon. During the one month period, devotes of the Buddhist faith help the monks to carry out their religious practice by making offerings of all their 9 requisites and other useful items.

Source: http://laos-adventures.com/page.asp?id=%7B4614FA47-8BAD-4899-80FF-9C9314BF0515%7D