An island built for it
Ayutthaya sits where the Chao Phraya, the Lopburi and the Pa Sak meet, and the old city was cut off as an island on purpose, a defensive moat that was also a port. On Loy Krathong that geography pays off differently: there is water on every side of the historic park.
The krathong itself is a small float, traditionally banana trunk and folded leaves, carrying a candle, incense and a coin. It is set on the water to carry off the past year and to apologise to the river for the use made of it.
What to look for
The ruins are lit for the festival, and the combination of brick prang against water and candlelight is the reason people travel for this one rather than joining it at home. Wat Chaiwatthanaram, on the west bank, is the view most photographed and the most crowded.
Styrofoam floats are still sold and still a problem; bread and banana-trunk versions are widely available and are what the clean-up crews would rather you bought.
Timing
It falls on the November full moon, so the date moves each year. The lighting of the ruins usually runs for several evenings around it, which means the night before or after the full moon gives you most of the spectacle with a fraction of the crowd.
