Well that was crazy.
We walked over from our hotel (by the way, we're staying at the FX Hotel Royal Panerai - it's awesome and it's absolutely perfectly located for all the Yi Peng/Loi Krathong celebrations) to the river where we saw a bunch of people gathering for the festivities. We planted ourselves by a barrier so we would have front row seats for the parade. We had to wait a little longer than expected, but it was fun once it came through. Floats, fire breathers, dancers, and music.
After the parade, we walked down to the river's edge and sat watching people light fireworks - some cool ones but mostly bottle rockets. Although I suppose that nobody calls them bottle rockets here because they definitely do not use a bottle to launch them. They just hold them in their hand and then let it go when it starts shooting sparks.
You notice instantly how little safety precautions people take with fireworks. From people holding fireworks, to shooting them deliberately at passing boats, to the idiot kids that light an M80 and set it on a post right next to all of us (including themselves) - we were deaf for a few minutes. And then you had a few people on the opposite bank of the river shooting bottle rockets at us.
There were also plenty of people launching floating lanterns, but even those were getting caught on limbs and wires and burning above people, so you had to keep an eye out for those too.