The story of 12 boys and their soccer coach trapped in a flooded cave in Thailand gripped the world and had barely ended last year when filmmakers began clamoring to get the nail-biting drama onto screens. Director Tom Waller’s “The Cave” premieres in South Korea this weekend. Waller filmed at the exterior of the actual Tham Luang cave and in water caves around the world. Waller even had more than a dozen rescue personnel play themselves. “That was really very emotional for some of them because it was absolutely real,” he said.