In the heart of Thailand, an autistic girl named Zen discovers she possesses an incredible ability to mimic martial arts moves she sees on television and from watching the training next door at the Muay Thai academy. Growing up beside her sick mother, Zin, who is gradually succumbing to cancer, Zen develops a deep bond with her childhood friend, Moom, who helps collect money owed to Zin from her former life connected to the criminal underworld. Unfortunately, due to Zin's past relationship with a Japanese gangster, Yakuza member Masashi, and her subsequent affair with the small-time Thai gangster No.8, she is ostracized and left to face her challenges alone, relying heavily on her daughter's burgeoning skills for protection.

As Zen's mother's condition worsens, the need for an expensive medical treatment enhances Zen's determination to help, leading her and Moom to seek out those who owe money to her mother. Using a ledger with the names of debtors, they undertake a perilous journey collecting dues. This quest draws the attention of No.8, now a formidable figure in the criminal underworld, who sees Zen's actions as a threat. Zen's unique talents are put to the test as they encounter increasingly violent and dangerous situations, sparking a spiral of confrontations. Despite her mother's tumultuous past, Zen remains unfazed, her martial arts prowess a beacon of hope against the looming adversity presented by her family's dark affiliations.