The movie combines horror, suspense, social satire and humor in the story of a man of faith transformed into a vampire by a medical experiment gone wrong.
If pushed, Park calls the film "a vampire romance." But he doesn't like labels.
"I didn't set out to make a vampire film that would infuse fresh new blood into the genre," Park said through an interpreter. "I didn't want to make a completely new vampire film. I wanted to make a completely new film with priests in it."
Park is one of South Korea's most respected directors, with a resume that includes the gory "Oldboy," which won Cannes' second prize in 2004.
"Thirst," co-produced by Universal Pictures, is the first Korean film made with Hollywood backing.
The central character's faith in God makes "Thirst" the story of a spiritual struggle. Priest Sang-hyung (Song Kang-ho), experiences a crisis of faith and morality when he discovers he must drink human blood to survive.
"This is a man who believes in God, who turns into something more akin to a devil or a monster," Park said. "This downfall causes him to question why this has happened to him."
At the same time, "he struggles to take responsibility for what has happened."
The film mines humor from the hero's attempt to avoid killing anyone to slake his bloodlust — he takes to drinking from the IV tube of a comatose hospital patient. It's also a serious portrait of a man questioning the God he has always believed in.
"This is a character who is acutely aware of the unethical aspects of drinking someone else's blood," Park said. "He recognizes this as bad behavior."
Newly awakened to carnal desires, Sang-hyung falls in love with unhappy housewife Tae-ju (Kim Ok-vin), and the pair embark on a passionate romance that leaves her, too, with a taste for blood. While Sang-hyung struggles, Tae-ju embraces her new identity, dispatching victims with gusto.
"She says 'This is not what I wanted, to become a vampire, but since I am one, I am going to enjoy it.' She almost feels a sense of liberation," Park said.
"Thirst" moves away from the revenge theme of Park's best-known films, the trilogy that included "Lady Vengeance" and "Oldboy." His last feature, "I Am a Cyborg, But That's OK," was a romantic comedy set in a mental institution.
Park says "Thirst" is "a culmination of all my previous work."
"All contained aspects of religion, aspects of a desire for redemption," he said. "This is a film where finally they are at the fore."