Technically, Loy Krathang doesn't start until Sunday night, but we went downtown on Saturday to see what was going on. Loy Krathang is the name for these little bamboo rafts that the Thais release into the Ping River.
The origins are probably rooted in animism, where the Thais worshipped a river goddess and asked for her blessing. The holiday took on Buddhist overtones, and the rafts are lit to honor Buddha. The general belief is that when the rafts are released they take away the badness in a person and/or they grant a wish. In this, Loy Krathangs are similar to Khom Loys, and there were plenty of those still being released.
Whatever one believes, Loy Krathang is an excuse to have fun. What water is to Songkran, fireworks are to this holiday. The uncontrolled lighting of fireworks in crowded areas is rather dangerous, but perhaps that's part of its appeals.