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Thailand’s Most Dangerous Female Serial Killer: She Murdered 14 of Her Friends Over Debt and Gambling

May 12
6 min read

Updated: Jun 19

The “Am Cyanide” Case: Thailand’s Alleged Serial Killer and the Mysterious Cyanide Murders

In one of the most shocking criminal cases in modern Thailand, a woman accused of poisoning her friends with cyanide became known nationwide as “Am Cyanide.” The case exposed a disturbing pattern of betrayal, greed, gambling addiction, and carefully planned murders that may have continued for nearly eight years

The suspect, Sararat Rangsiwuthaporn, was accused of targeting people close to her — friends, former partners, and acquaintances — before allegedly poisoning them and stealing their valuables. Thai investigators believe she may be responsible for up to 14 deaths between 2015 and 2023, making her one of the most notorious suspected serial killers in Thai history.

Who Is Sararat Rangsiwuthaporn?

Sararat Rangsiwuthaporn, often called “Am Cyanide” by Thai media, was a woman in her mid-30s living what appeared to be a normal life. Behind the scenes, investigators say she suffered from severe financial problems connected to online gambling and heavy debt.

Police stated that she frequently borrowed money from people close to her. According to investigators, when victims demanded repayment or when she wanted their property, she allegedly poisoned them using cyanide. After their deaths, money, jewelry, phones, and personal belongings often disappeared. (theguardian.com)

Authorities later discovered financial links between her bank accounts and online gambling transactions worth millions of baht. The court also heard evidence that she had accumulated significant debts before several suspicious deaths occurred.

How the Case Began

The investigation exploded into public attention in April 2023 after the sudden death of Siriporn Khanwong, also known as “Koy.”

Siriporn traveled with Sararat to Ratchaburi to participate in a Buddhist ritual involving releasing fish into the Mae Klong River for good luck and spiritual protection. Shortly after eating with Sararat, Siriporn suddenly collapsed and died near the riverbank.

Investigators became suspicious because:

Sararat reportedly did not try to help her friend.
Siriporn’s valuables disappeared after her death.
An autopsy later found potassium cyanide in her body.

This discovery triggered a deeper investigation that uncovered a shocking pattern of similar deaths connected to Sararat dating back to 2015.

The Victims

Police connected Sararat to numerous suspicious deaths across Thailand. Most victims reportedly knew her personally. Many had loaned her money, traveled with her, or met her shortly before dying suddenly from unexplained causes.

Among the reported victims were:

Siriporn Khanwong — the first confirmed murder case brought to trial.
Nipa Saenchan — a police officer allegedly poisoned in 2023.
Suthisak Poonkwan — Sararat’s former boyfriend, whose death raised further suspicions.
Sawittree Budsrirak — one of several women allegedly connected to the poisonings.
Monthathip Khao-in — another suspected victim linked to Sararat.

One alleged victim survived, helping investigators understand how the poison may have been administered. Police claimed Sararat sometimes used food, drinks, or herbal capsules to deliver cyanide.

The Poison: Cyanide

Cyanide is one of the deadliest fast-acting poisons known. It prevents the body’s cells from using oxygen properly, causing rapid organ failure.

Symptoms include:

dizziness
vomiting
breathing difficulty
chest pain
seizures
sudden collapse

In large doses, cyanide can kill within minutes. Investigators found “fatal levels” of potassium cyanide in some victims’ blood, stomachs, and organs.

Thai authorities later discovered traces of cyanide in Sararat’s vehicle and evidence suggesting she had ordered the chemical before several deaths occurred.

The Investigation

As families of victims came forward, police reopened older cases previously believed to involve natural causes. Investigators noticed disturbing similarities:

sudden deaths after meals or drinks
victims connected personally to Sararat
missing valuables after death
financial disputes before the incidents

Thai police eventually filed around 80 criminal charges against Sararat, including premeditated murder, attempted murder, theft, and forgery.

Authorities described the case as one of Thailand’s largest serial poisoning investigations in decades.

The Trial and Death Sentence

In November 2024, a criminal court in Bangkok found Sararat guilty of murdering Siriporn Khanwong. She was sentenced to death in the first of multiple murder trials. (theguardian.com)

The court concluded that:

Sararat intentionally poisoned Siriporn.
She stole the victim’s belongings afterward.
Her actions before and after the death demonstrated planning and intent.

Siriporn’s mother emotionally stated after the verdict that justice had finally been served for her daughter.

The Role of Her Ex-Husband and Lawyer

The case expanded further when authorities accused Sararat’s former husband — a former police officer — and her lawyer of helping hide evidence. Both received prison sentences. (theguardian.com)

Investigators believed the ex-husband may also have helped Sararat after another suspected poisoning involving her former boyfriend.

Why the Case Shocked Thailand

The “Am Cyanide” case horrified the Thai public because the alleged victims were not strangers. Many were close friends or trusted companions. The murders appeared calculated, financially motivated, and hidden for years behind what seemed like ordinary sudden illnesses.

The case also raised questions about:

how dangerous chemicals were obtained,
how earlier deaths were overlooked,
and whether gambling addiction and debt pushed the suspect toward serial murder.

Even after the first conviction, Sararat still faced numerous additional murder trials. Thai media and international news organizations described the investigation as one of the darkest criminal stories in the country’s recent history.

Frequently Asked Questions About Thailand’s Most Dangerous Female Serial Killer

Who is Sararat Rangsiwuthaporn?

Sararat Rangsiwuthaporn, often called “Am Cyanide” by Thai media, was a woman in her mid-30s who appeared to live a normal life while allegedly poisoning people close to her with cyanide. Investigators found financial links between her bank accounts and online gambling transactions worth millions of baht.

Why was she nicknamed “Am Cyanide”?

Thai media gave her the nickname because her alleged method of murder was poisoning victims with cyanide — one of the deadliest fast-acting poisons known. It prevents the body’s cells from using oxygen properly, causing rapid organ failure and, in large doses, death within minutes.

How did the case come to public attention?

The investigation exploded into public attention in April 2023 after the sudden death of Siriporn Khanwong, who had traveled with Sararat to Ratchaburi for a Buddhist ritual releasing fish into the Mae Klong River. Investigators grew suspicious because Sararat did not try to help, the victim’s valuables disappeared, and an autopsy found potassium cyanide in her body.

How many victims were linked to Sararat?

Police connected Sararat to numerous suspicious deaths across Thailand dating back to 2015, with around 14 suspected victims in total. Most of them knew her personally — many had loaned her money or traveled with her — and one alleged victim survived, helping investigators understand how the poison was administered.

What was the suspected motive?

Police said Sararat frequently borrowed money from people close to her, and authorities uncovered financial links to online gambling worth millions of baht. According to investigators, when victims demanded repayment or when she wanted their belongings, the poisonings allegedly followed.

How did the investigation unfold?

As families of victims came forward, police reopened older cases previously believed to involve natural causes, noticing patterns such as sudden deaths after meals or drinks, missing valuables, and financial disputes. Thai police eventually filed around 80 criminal charges against Sararat, including premeditated murder, attempted murder, theft, and forgery.

What was the outcome of her first trial?

In November 2024, a criminal court in Bangkok found Sararat guilty of murdering Siriporn Khanwong and sentenced her to death in the first of multiple murder trials. The court concluded she intentionally poisoned Siriporn, stole the victim’s belongings afterward, and acted with planning and intent.

What roles did her ex-husband and lawyer play?

Authorities accused Sararat’s former husband — a former police officer — and her lawyer of helping hide evidence, and both received prison sentences. Investigators believed the ex-husband may also have helped her after another suspected poisoning involving her former boyfriend.

Why did the case shock Thailand?

The case horrified the Thai public because the alleged victims were not strangers but close friends and trusted companions, and the murders appeared calculated and repeated over years. It raised questions about how dangerous chemicals were obtained, how earlier deaths were overlooked, and whether gambling addiction and debt drove the crimes.

Does Sararat face additional trials?

Yes. Even after the first conviction and death sentence, Sararat still faced numerous additional murder trials, and Thai and international media described the investigation as one of Thailand’s largest serial poisoning cases in decades.