These are "aijai" women, people--most often women--who push carts through the streets of Phnom Penh calling "Aaaai-jaai" to let households know that they are coming through.  Some of them specialize in one sort of trash or another, but most will pick up newspapers, cans, bottles, plastics, or anything metal.  They weigh it on scales (hidden under the trash in this picture) and give a small amount, a few cents, for the trash, and then they push it to a large dumping center where they are paid for the whole cartload.  If they're lucky, they might earn a dollar or so a day.