Prajan Daeng

Doctor Sama was born on the night of the "Scarlet Moon," the same night a Sang (a mythical weretiger/spirit) slaughtered his parents. Sama survived only because a wandering monk and a local elder named Sri rescued him. However, the encounter left him cursed; he inherited the Sang’s spirit and is forced to transform into a beast every time the Red Moon rises.

The Curse and the Village

Sama returns to his home village to serve as a doctor, treating the locals by day. But when the Scarlet Moon appears, he loses his humanity and kills. One of his victims is Suea, the son of the influential Paoliang Det. Consumed by vengeance, Det hires skilled hunters to track the beast, only for them to be slaughtered. Eventually, he hires a master hunter named Chup. It is revealed that there are actually two Sangs: one is Doctor Sama, and the other is Yuso, the father of a local girl named Kalong.

The Search for a Cure

While Kalong is in love with Sama, his heart belongs to Parichat, a young schoolteacher who recently moved to the village. Sama desperately tries to concoct a medicinal cure to suppress his transformation, but every attempt fails.
Eventually, the secret to breaking the curse is revealed. To be free, Sama needs the help of a woman who fulfills specific mystical criteria:

• She must be born on the 9th day of the 9th month in the Year of the Tiger.
• She must be someone the Sang refuses to kill upon encounter.
• The ritual requires the Sang to sleep with this woman while in his beast form during a Total Lunar Eclipse on a Scarlet Moon night.

The Final Transformation

It turns out that Parichat is the chosen one. Not only does her birthdate match the prophecy, but she has encountered the Sang twice, and both times the beast spared her and retreated. With her love and bravery, Parichat helps Doctor Sama perform the ritual, successfully breaking the ancient curse and allowing him to live a normal life at last.