Thailand is eyeing a billion-dollar tourist bounce over the next five years from hosting Tomorrowland, which makes its Asia debut in December. An estimated 150,000 young ravers are expected to flood the resort city of Pattaya for the world’s largest electronic music festival. For years a touchstone of global tourism, the kingdom recently has seen its popularity wane as the strong baht deters some travellers while regional rivals Vietnam and Malaysia gobble up market share. To turn the trajectory...