Sararat Rangsiwuthaporn was born on March 12, 1987. She was married to a senior police officer, Police Lieutenant Colonel Withoon Rangsiwuthaporn, and by the time of her arrest she had run up substantial debts on credit cards and through online gambling. The Thai press calls her Am Cyanide, from her nickname Am and the poison she used.
The method was almost domestic in its simplicity. She borrowed money from people she knew, in some cases as much as 300,000 baht, about nine thousand US dollars. When they asked for it back she arranged to meet them, gave them what she said were herbal capsules, and took their jewelry and mobile telephones after they collapsed. The deputy national police chief, Surachate Hakparn, put it in one sentence: she asked people she knew for money because she had a lot of credit card debt, and if they asked for it back she started killing them.
The case surfaced on April 14, 2023, when Siriporn Khanwong, known as Koy, went with her to the Mae Klong river west of Bangkok to release fish as a Buddhist merit-making ritual. They stopped to eat. Siriporn collapsed and died, and cyanide was found in her body. Her bag, her money and her telephone were gone. Sararat was arrested on April 25, 2023.
Once the poison was identified, police went back through unexplained deaths among her acquaintances and found a pattern reaching to 2015. Fifteen people had been given the capsules and one had survived. Investigators recovered fingerprints and other evidence from her vehicle. By the end of the investigation she faced fourteen counts of premeditated murder and about eighty charges in total, including poisoning, theft and forgery, which police described as a record in Thai criminal history. Surachate remarked at the press conference that even Jack the Ripper had not killed this many, and announced that Thailand would tighten controls on access to cyanide.
The counts in this case need care, because a great deal of the international coverage does not take it. Fourteen murders were charged, and each is tried separately. Seven of the fifteen prosecutions have been decided. She was convicted on November 20, 2024 of the murder of Siriporn Khanwong and of robbing her of property worth more than four thousand US dollars, and sentenced to death; the judge described a gambling addict who had turned to murder and robbery to clear her debts. She was convicted again in February 2026, of the murder of the police officer Nipa Saenchan, and again on April 30, 2026, of the murder of Police Captain Sukanda Wimolman; in both the court pronounced death and then reduced it to life because her testimony had been of some use to the proceedings. A fourth conviction on August 25, 2026, for the murder of her creditor Darinee Thepthawee, carried a death sentence that stands. Against those four she has three acquittals, the courts finding in each that nobody had seen her administer the poison and that the evidence did not close the gap. Several outlets reported the first verdict as a conviction for fourteen murders. It was not, and the arithmetic has not simplified since: four are proved, three have failed in court, and seven are still to be heard.
Two other people were prosecuted around her. Her former husband was sentenced to sixteen months for concealing evidence and helping her avoid arrest, and was separately alleged to have assisted in the death of a former boyfriend of hers, Suthisak Poonkwan. Her lawyer, Thanicha Aeksuwannawat, was also accused of helping to conceal evidence. Both Sararat and her husband denied the allegations.
The reason the case held Thailand's attention was not only the number. It was that the victims were friends, that the deaths had passed as natural for eight years, and that the accused was the wife of a police officer. It is the largest series of poisonings ever prosecuted in the country.