HANOI — About a 30-minute drive northwest of downtown Hanoi on Friday, the entrance to Thang Long Industrial Park came into view after crossing Nhat Tan Bridge, which connects Hanoi with Noi Bai International Airport. At factories throughout the industrial complex, Vietnam’s red flag with a yellow star flew alongside Japan’s flag. Developed by Japanese trading house Sumitomo Corp., the industrial park is, in effect, a cradle of Japanese manufacturing. Beyond the entrance, signs for more than 100 Japanese companies, including Panasonic, Canon and Fujitsu, stretched across a 2.73-million-square-meter site. Some 60,000 Vietnamese workers stream into the complex every day. A female worker at Panasonic said Japanese companies were regarded as more stable, even though Chinese and Korean firms paid higher wages, adding that many employees stayed for years. “Many skilled workers have been here for more than 10 years, and new employees join every month, so the atmosphere is good,” she said. Nguyen Thanh, 32, a management employee at the industrial park, said it had reached full occupancy