Spilotes (Pseustes) sulphurus
About six feet long, this arboreal snake is compressed laterally, which helps it thrust out over long distances between tree branches without drooping. In the 4th photo, you can really see how flat it makes itself when going for distance -- look at the difference between #3 and #4. The complex green/yellow pattern reminded me of a design woven in fabric. This is not a venomous snake although it inflates its throat to look bigger and meaner. It eats birds and rodents.
This snake fell about 30 feet down out of a tree just behind us as we were walking through the humid rainforest on the north bank of the Amazon River.
It was easily caught, and was relatively calm, apparently unhurt by its fall.