Deep in the Jungle(2008)

Original title: ปาฏิหาริย์รักต่างพันธุ์

Nawin, a secret agent, goes rogue to rescue a mysterious woman, Jin, from the private military force that abducted her. They flee to her birthplace, pursued by the force's captain, and also by Jin’s brother, a killer capable of transforming into a giant serpent.