On the full moon of the 12th Thai month, millions of small lotus boats carrying candles are floated on rivers and canals.
'Loy' means 'to float', 'Krathong' is the small banana-leaf raft decorated with flowers, candles, and incense — floated to pay respect to the water spirits and let go of bad luck.
The Chao Phraya and surrounding canals fill with glowing krathong; Asiatique, Wat Pho, and the Grand Palace area are popular launch spots.
Full moon of the 12th Thai month — usually November; exact date changes annually.
In Chiang Mai (same night), sky lanterns (khom loi) are released — the sky fills with floating lights; some Bangkok events also release lanterns.
Traditional krathong use banana leaves and flowers; modern versions use bread (biodegradable); sold everywhere near the river the week of the festival.
Riverside temples and piers along the Chao Phraya offer the most atmospheric viewing — arriving an hour before dusk secures a good spot before the crowds build.
Traditional banana-leaf krathong are genuinely biodegradable; bread versions are marketed as fish-friendly, while foam or plastic krathong are discouraged and increasingly hard to find as awareness grows.