As the repercussions of past events unfold, Tien (Tony Jaa) finds himself trapped and helpless against the ruthless soldiers commanded by Lord Rajasena. A brief but futile struggle occurs, as his captors attempt to subdue him with wooden rods, ultimately breaking both his spirit and crippling his body. Simultaneously, a mysterious affliction befalls the village of Kana Khone, compelling Master Bua (Sarunyu Wongkrachang) to embark on a perilous Buddhist pilgrimage to uncover the cause. His journey reveals a shocking truth: the curse originates from Bhuti Sangkha, the dark mystic who had previously defeated Tien.
Haunted by visions of his royal predecessor, whose untimely end serves as a grim reminder of his treachery, Lord Rajasena's tortured psyche becomes further unsettled. While he slumbers, remnants of the Pha Beek Khrut bandits try to rescue Tien from captivity, only to meet a brutal end at the hands of Bhuti Sangkha’s malevolent influence. The dark mystic has dual motives; he declines Lord Rajasena's offer for employment and proposes to lift the curse with suggestions that Tien is somehow intertwined with this supernatural affliction.
Upon the arrival of a messenger from the Ayutthaya Kingdom, who brings a pardon for Tien, Lord Rajasena’s rage escalates. Believing betrayal is afoot, he sends assassins to eliminate Tien; however, their efforts are thwarted by the brave sacrifice of the royal messengers. When Master Bua returns, he brings disheartening news: Tien's suffering is a result of negative karma, triggering the village to unite in a mission to restore him through collective merit-making.
The culmination of this effort results in the creation of the sacred Ong Bak Buddha, which ultimately revives Tien. Yet, upon awakening, he realizes that his physical form is still marred by the scars of his ordeal. Overwhelmed by this painful reality, Tien contemplates self-destruction; however, Master Bua intervenes, offering words of wisdom that reignite hope within him.
Embarking on a journey of recovery, Tien engages in rigorous meditation and self-taught physical therapy at a temple. As he gradually regains his strength, he is graced by the presence of Pim; the two share a ritual dance before coming together in an embrace. Master Bua reminds Tien of the significance of Dharma, encouraging him to transform his foes into dance partners, which inspires him to develop an innovative fighting style that beautifully blends martial arts with the art of dance.
Determined to lift the curse plaguing him, Lord Rajasena ventures to Bhuti’s deserted stronghold, only to uncover that Bhuti himself orchestrated the affliction in a nefarious plot to usurp the throne. A fierce confrontation ensues, wherein Rajasena battles Bhuti’s legion but ultimately meets his end at Bhuti's hand. Before he dies, however, Rajasena places a curse upon Bhuti, mirroring his own suffering. Meanwhile, Bhuti sends his minions to eliminate Tien, but he proves more than capable of facing them.
When Tien learns that the village lies in ruins and its inhabitants have been taken to Bhuti's palace, where horrific elephant slaughters occur, he seeks guidance from Master Bua. He learns he has been chosen to stand against ignorance, and with newfound resolve, he prepares to confront Bhuti. In their encounter, Bhuti feeds off Tien's negativity and invokes a celestial eclipse. Pim, fiercely loyal, arrives, only to incite Bhuti’s wrath as he strikes her down. This devastating loss unleashes Tien's fury, compelling him to forge a path through Bhuti’s ranks with relentless ferocity.
Despite Tien's valor, Bhuti proves to be a formidable foe, plunging a spear into Tien’s chest. As Tien's life begins to slip away, memories of Bua’s teachings flood his mind, revealing that the entire battle, including Pim’s tragic fate, was merely an elaborate illusion. Empowered by this realization, Tien obliterates Bhuti’s powers and dispels the eclipse, igniting Bhuti's rage, which becomes his undoing. Their ferocious struggle culminates on a royal ledge, where Tien gains the upper hand, ultimately sending Bhuti over the edge to meet his demise at the hands of an enraged elephant. The elephant's fallen form eerily resembles the revered one-tusked Ganesha, a powerful symbol of victory.
The film concludes with Tien, Pim, and the surviving villagers paying homage to the sacred Ong Bak, marking a hopeful new beginning for all.
