Manufacturing in 3rd world countries work best in three situations. High-labor assembly work. Environmentally damaging factories that produce an exportable product. And commodity factories with a high raw material to finished good shrinkage.
Most manufacturing benefits from low wages in the producing country vs the consuming country and is the most common. For example, cell phones and appliances are assembled in China and Mexico, then exported to the USA and Japan. But the raw-materials that go into these appliances are typically produced in advanced fabrication factories in 1st world countries. A large portion of the microchips and fabricated parts used in microelectronics are produced in Korea, the USA and Japan.
Poisonous factories produce a product that is in demand, but difficult to get regulators to approve in 1st world countries. High-shrinkage products in 3rd world countries are by definition labor intensive. For example, aluminum smelting (aluminum to ore is a low ratio). An example of a high-shrinkage product that is not labor intensive is alcohol.
Assembly factories - electronics, toys, small consumer goods, jewelry, art, clothing
Poisonous factories - batteries, small-batch chemical processing, radioactive (re)processing
Commodity factories - smelters, specialty products (cheese, tequila, meat processing)