“The Betrayal” takes the audience on a harrowing journey with the Phrasavath family (which was split asunder at the end of the Vietnam Wa) from Laos to New York. Thavisouk (Thavi) Phrasavath, one of the sons, tells the story from a first-person perspective. Self-consciously poetic and shot within a luscious inch of its life, the film’s also an engrossing heartbreaker: a family saga that spans continents, political administrations, and decades of travail to arrive at a harder, wiser place.