The bin truck turned up in the car park, and I was amazed when I realised that the team of people hanging off the back of the truck weren't putting rubbish through the crusher at the back of the truck, but they were sorting the contents of every bin into recyclable categories. There were a series of sacks tied strategically around the back of the truck and the sorters were categorising every item and placing into the correct sack. Only genuine rubbish went through the actual trash crusher into the back of the truck. As each category of sack was filled, it was sealed and placed on top of the truck, and a new sack took its place. My stomach did turn a little when one of the sorters found his breakfast, and he took a standing meal break

I don't know if this is standard for all waste collection trucks (ours usually turns up in our street after dark), but it would explain why some items (I wrote about bags of dog waste before) are left on the ground beside the bins.
I must say, I was very impressed with this recycling effort in Thailand.