When the monsoon ends, the Tonlé Sap stops running inland and turns back toward the Mekong. Cambodia marks the turn with three days of boat racing in front of the royal palace in Phnom Penh, lit barges on the water at night, and flattened rice eaten under the full moon.
A river that changes its mind
For half the year the Mekong pushes so hard that it forces the Tonlé Sap river backwards, up into the great lake, which swells to several times its dry-season size. When the monsoon ends the pressure drops and the river turns around and runs back down to the Mekong. Bon Om Touk is held at that moment, on the full moon of the Khmer month of Kadeuk.
Boat racing here is old. It is recorded in Cambodia at least from the reign of Jayavarman VII in the late twelfth century, and it is usually read as remembering the Khmer naval victory over the Cham. The racing boats are long, narrow pirogues, painted with eyes at the bow so that the boat looks alive, and a winning crew may be sixty-four to seventy-seven rowers strong. Each is entered by a community, and the villages bring them to the capital for the three days.
The night side
By day the races run on the river in front of the royal palace. At night the water carries the loy pratip, illuminated floats sent out by the ministries in honour of the water goddess. On the night of the full moon comes the sampeah preah khae, the salutation to the moon, and after it the ak ambok: flattened rice pounded from the new crop, eaten with banana and coconut, sometimes pushed into the mouth in handfuls by people who are laughing at you.
Going
In 2026 the festival is on 23, 24 and 25 November. Phnom Penh takes in a large part of the country for it; the riverbank is free to stand on, and the hotels along Sisowath Quay are booked months ahead. Confirm the days before you travel — they move with the moon, and the festival has been cancelled in some years for flooding, for mourning and for public health.
When it happens
The festival sits on the full moon of the Khmer month of Kadeuk and runs for three days, usually in November. In 2026 it falls on 23, 24 and 25 November, with the full moon on the middle day.
- November 23 – 25, 2026Officially announced
Visiting with respect
Good to know
- Watching from the riverbank is free, and most of Phnom Penh watches from there. Come early for a place at the rail and expect to stay where you are put.
- Each boat belongs to a commune, a pagoda or a province, and its crew has trained together for months. Applaud the boats, not only the winner.
- The evening of the full moon is a home occasion as much as a public one. If you are invited to eat ambok, eat it with the banana and the coconut, the way it is handed to you.
Avoid
- Do not stand on unofficial pontoons, jetties or boats moored along the bank.
- Do not swim in the river during the races. The current at the turn of the water is strong and the racing lanes are busy.
Stay safe
- In 2010 a crowd crush on the bridge to Koh Pich, Diamond Island, killed 351 people and injured hundreds more. The authorities now manage the flows tightly, and police lines are to be followed without argument.
- Thieves on motorbikes cut bag straps and snatch phones along the Phnom Penh riverfront. Carry as little as you can.
- It is hot, the crowd is dense and there is little shade. Carry water and agree on a meeting point.
Sources
This entry was written from the following sources.
- Bon Om ToukWikipedia · read September 24, 2026
- Khmer calendar — festivals and holidays, November 2026Khmer Calendar · read September 24, 2026
- Cambodia travel advice: safety and securityUK Foreign, Commonwealth & Development Office · read September 24, 2026
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