Dek Seple follows Tin, a troubled young man who was separated from his family as a child and forced into a life of crime by a ruthless street gang. When a failed robbery leads him to seek refuge at a local school, Tin forms a life-changing bond with Kobkul, a kind student who sees his potential, and Kru Sak, a devoted teacher who fights to reform troubled youth. Unbeknownst to them, Kru Sak is actually Tin's long-lost biological father, setting off an emotional journey of survival, redemption, and a young man's struggle to break free from his dark past.