BANGKOK, Thailand — A surprise cinematic breakout from China has defied industry expectations this year, topping domestic box office charts and rolling out across international markets as a centerpiece of Beijing’s growing soft power push. What makes *Dear You*’s success all the more remarkable is its core creative choice: nearly the entire film is performed in Teochew, a regional southern Chinese dialect largely unintelligible to most Mandarin-speaking Chinese audiences, who rely on subtitles to follow the story.