- Marsha Wattanapanich as Pim and Ploy
- Vittaya Wasukraipaisan as Wee
- Ruchanu Boonchooduang as Pim’s and Ploy’s mother
- Hatairat Egereff as Pim, age 15
- Rutairat Egereff as Ploy, age 15
- Chutikan Vimuktananda as Pim, age 7
- Chayakan Vimuktananda as Ploy, age 7
- Namo Tongkumnerd as Wee, age 15
Alone is a 2007 Thai horror film directed by Banjong Pisanthanakun and Parkpoom Wongpoom, a duo whose debut film, Shutter, was a box-office smash in Thailand and other Asian countries. Alone stars Thai-German pop singer Marsha Wattanapanich in her first film role in 15 years. Pim was born as a Twin, conjoined at the stomach with her sister, Ploy. Pim was very sweet and protective to Ploy.However, it was Ploy who threw rocks at a group of children who were taunting them. While they were staying in a hospital, Pim and Ploy met a boy named Wee. Although both loved him, Wee only returned Pim’s affections, which made Ploy angry and jealous. Finally Wee recovers from his illness and was able to leave. As he is getting into the car, Wee decided he wanted to see Pim one last time. Since the twins’ room was on the second floor, he decides to call to her. As much as Pim wants to see Wee, Ploy would not get out of bed. Wee is upset and leaves. Angry and in tears, Pim demands that she and Ploy be separated. The twins had an operation to separate them, but Ploy did not survive.
Several years later Pim, who is now living in South Korea and is dating Wee, receives a phone call from Thailand that her mother has had a stroke. When Pim and Wee return to Thailand, Ploy comes back to haunt her. Curious, Wee looks into Pim’s family affairs. In a stroke of irony, Wee learns that Pim is actually Ploy. Revealed in a flashback, Ploy strangled Pim in a jealous rage after Pim demanded they be separated. In order to save Ploy’s life, doctors had to amputate Pim’s corpse from Ploy. Ploy assumed Pim’s identity in order to be with Wee. Throughout the film, Pim’s ghost was actually trying to tell Wee of this. Ploy’s mother knew of her actions as well, tried to tell him, but was unable to talk due to her weakened state.
After confronting Pim, Ploy takes Wee hostage, but not before killing her mother. However, Wee escapes, and the ensuing fight with Ploy causes the house to catch on fire. Wee escapes, but a shelf falls on Ploy. Trapped underneath, Pim’s ghost confronts and holds her down, taking Ploy with her as burning debris rains down around them. In the end, Wee visits the twins’ grave, apologizes, and places a necklace on their tombstone.