Clocking in at under 18 minutes, “A Letter to Uncle Boonmee” is nevertheless a major work by Thai writer-director Apichatpong Weerasethakul, not merely a nifty preface to Uncle Boonmee Who Can Recall His Past Lives, for which Apichatpong won the 2010 Palme d’Or at Cannes. Its brevity, moreover, helped impose a powerful rigor on the material. […]