When a shot rang out at the Debsirin Nonthaburi School on the outskirts of Bangkok on Friday morning, 14-year-old Khim and her classmates peered over a balcony to see if the noise had come from a construction site.But more loud bangs followed, until a teacher ushered them all into a classroom, checked a messaging group and confirmed to the now terrified students: there was an active shooter in their building.“I heard multiple gunshots and felt like we weren’t going to survive,” Khim, who...