Miss Happy stars Pancake Khemanit as a happy-go-lucky woman named Happy, who often annoys her best friend Golfie (Ben Chalatit). Unfortunately, Happy is diagnosed with having an irregular heartbeat that will likely cause her death within a month. In an effort to survive, Happy looks up information and finds a YouTube video made by Tul, played by Jitpanu Klomkaew (Ball). Tul's video claims that Happy can stay alive if she dances in the way shown in the video.
