Thai Union Manufacturing TUM is a subsidiary of Thailand’s largest company processing and manufacturing fish products, Thai Union Frozen Products PCL. In the factories of TUM, 400 tons of tuna is processed every day. According to TUM, its factory complex is the biggest tuna fi sh processing plant in Asia, and it employs around 8,500 people. The factories are situated in Samut Sakhon province in Central Thailand. Half the factory workers are citizens of Thailand, and the rest are migrant workers from Myanmar and Cambodia.