Pchum Ben Day or All Soul Day

Running for 15 days, usually from the end of September into October, this festival is dedicated to blessing the spirits of the dead and is one of the most culturally significant in Cambodia.  The exact date defers year to year as determined by the lunar calendar.  Each household visits their temple of choice and offers food to the monks.

Offering of food is a meritorious act and is one of the oldest and most common rituals of Buddhism. During the Pchum Ben festival, people bring food to the temple for the monks and to feed hungry ghosts who could be their late ancestors, relatives or friends. Pagodas are usually crowded with people taking their turn to make offerings and to beg the monks to pray for their late ancestors and loved ones. Many remain behind at the temple to listen to Buddhist sermons.

Footnote:-

"Hungry ghost" is one of the six modes of existence in the ‘Wheel of Life’. Hungry ghosts or ‘Preta’ which means ‘departed ones’ in Sanskrit, are pitiable creatures with huge, empty stomachs and pinhole mouths; their necks are so thin they cannot swallow, so they remain hungry.  It is believed that beings are reborn as hungry ghosts because of their greed, envy and jealousy.

Cambodians leave food offerings on altars and around temple grounds for hungry ghosts.  Pchum Ben is a festival that features food and entertainment for such hungry ghosts.

Sourced: tourismcambodia.org