The Smiling Poisoner: Unmasking Thailand's Chilling Cyanide Serial Killer

Have you ever imagined that a long-time friend with a warm smile, or even the person you love most, could one day become the demon who takes your life? It sounds like the plot of a horror film, yet it unfolded with terrifying reality under the bright Thai sun. A serial murder case that shocked the nation, with up to 15 confirmed victims, possibly more, and the perpetrator? A seemingly ordinary pregnant woman. How did she do it? And what drove her to ruthlessly murder those closest to her? Brace yourself, the twists, turns, and sheer darkness of this case will defy your imagination.

Murder by the River of Merit

The story begins on April 14, 2023. During the Songkran holiday, 32-year-old businesswoman Siriporn Khanwong and her friend, Sararat Rangsiwuthaporn, met at a temple by the Mae Klong River in Ratchaburi province to release fish for good merit – a traditional act of kindness.

Security footage captured them: Siriporn carrying the bag of fish, while Sararat, 36, looked down at her phone. As they walked along the riverbank, Sararat appeared to say something to Siriporn before quickly walking across the road alone, glancing around, leaving Siriporn to continue towards the river.

Moments after Siriporn reached the water's edge, the unthinkable happened – she suddenly collapsed, unconscious. Bystanders rushed her to the hospital, but she was pronounced dead due to "sudden heart failure."

How could a young, healthy woman in the prime of her life suddenly die from heart failure? Siriporn's family couldn't accept this explanation and insisted on an autopsy. Their decision opened Pandora's Box. The forensic examination revealed traces of a lethal chemical in Siriporn's blood – cyanide! This was clearly no accident; it was murder.

Who Was the Killer? The Finger Points to the "Best Friend"

Police immediately focused on Sararat, who was with Siriporn at the time of her death but whose behavior raised alarms.

The suspicions mounted:

Strange Actions: CCTV footage showed Sararat separating from Siriporn, walking across the road, and looking around as if waiting for something to happen.

Callous Indifference: When Siriporn collapsed, strangers rushed to help, but Sararat, her supposed friend, merely glanced from a distance before driving away. She didn't call for an ambulance or accompany her to the hospital.

Missing Valuables: Siriporn's designer handbag, two mobile phones, and approximately 40,000 Thai Baht (around $1,200 USD) in cash vanished after her death.

Initially questioned by police, Sararat denied being with Siriporn that day. Only when confronted with the surveillance footage did she change her story, admitting they went to release fish together but claiming she left early due to an urgent matter. She professed ignorance about Siriporn's death and denied taking her belongings.

The Tip of the Iceberg: More Mysterious Deaths Emerge

Siriporn's case, widely reported by the media, sent shockwaves through Thailand. More terrifyingly, people began coming forward, reporting that their own family members or friends had also died suddenly from "heart failure" shortly after meeting or having contact with Sararat.

As police dug deeper, the pieces fell into place, revealing a horrifying pattern. Between 2020 and 2023, at least 14 individuals who had connections (mostly financial) with Sararat died under similar, abrupt circumstances. The victims included her ex-boyfriend, Suthisak Poonkwan, and at least two police officers.

These victims shared several characteristics:

Most were aged between 30 and 50 and were in good health.

Their cause of death was often attributed to heart failure or similar sudden illnesses.

They all had financial dealings with Sararat, or Sararat stood to gain financially from their deaths.

Unmasking the Monster: The Double Life of an Ordinary Housewife

Who exactly was Sararat Rangsiwuthaporn? She graduated from university in 2009 with a degree in Public Relations and briefly worked as an insurance agent. She married a high-ranking police officer, Witoon Rangsiwuthaporn, had two children, and lived in police housing. To the outside world, she appeared to be part of a happy, middle-class family.

But beneath the gentle housewife facade lurked a dark secret. Police discovered Sararat had divorced her police officer husband and was drowning in massive credit card debt. Her new boyfriend, Suthisak, died in 2022 shortly after visiting a temple with her to make merit. His symptoms? Sudden nausea and vomiting, followed by death, also attributed to heart problems. Suthisak's unsuspecting family even gave Sararat his money and gold jewelry after his death, hoping she would raise their unborn child (she was pregnant with his baby at the time) well.

Potassium Cyanide: The Silent Killer

The investigation took a crucial turn when a friend of Suthisak, suspicious about his death, secretly searched the home Suthisak shared with Sararat. In a hidden corner, he found a white bottle labeled "UN1680". Police analysis confirmed the innocuous-looking white powder was the deadly poison, potassium cyanide.

Potassium cyanide is familiar to fans of detective stories. It's typically a white crystalline powder or granule, sometimes with a faint bitter almond smell (though not everyone can detect it), and easily dissolves in water. It's extremely toxic, fatal even in tiny doses. It rapidly inhibits cellular respiration, causing tissue hypoxia, affecting the central nervous system and heart, ultimately leading to death from respiratory failure or cardiac arrest. Because its symptoms mimic a heart attack and it metabolizes quickly in the body (around 80% disappears within 24 hours), it's difficult to detect unless an autopsy is performed promptly, making it Sararat's perfect murder weapon.

Even more alarmingly, despite being a controlled substance in Thailand, illegal to purchase or possess without authorization, Sararat easily bought it online. Police discovered over 100 other individuals had also purchased cyanide online, including Thai actress Ice Preechaya (who claimed she bought it to deal with lizards and snakes in her home).

Murder for Money: A Frenzied Killing Spree Driven by Greed

Sararat's motive became chillingly clear: money. She employed various schemes to extract funds from her victims:

Loans: Borrowing money from close friends, promising high returns, then poisoning them when they asked for repayment. Kantima Paesa-ard, who luckily survived, is an example. She lent Sararat 250,000 Baht and was poisoned with "herbal medicine" for COVID after requesting repayment. She survived only because severe vomiting expelled the poison.

Rotating Savings Schemes (Pia Huei): Sararat organized a popular type of informal savings group common in Thailand. In the group she ran, with 7 members (including herself), police found that besides Sararat and one missing person, the other 5 members had all died of sudden heart failure. Sararat allegedly pocketed all the pooled funds.

Insurance Fraud: Using her past experience as an insurance agent, she convinced wealthier victims to buy life insurance policies with seemingly high payouts, then forged documents to make herself the beneficiary.

Car Pawn Loans: She persuaded victims in financial difficulty to pawn their cars for cash. Once they received the money, she poisoned them and kept both the cash and the vehicle. Nittaya Kewsuwan, who died in 2020, was a victim of this scheme; the 150,000 Baht from pawning her car disappeared after her death.

Police estimate Sararat illegally obtained as much as 78 million Thai Baht (approximately $2.275 million USD) through these horrific means. The money was transferred through her bank accounts to over a dozen other individuals, whom police are investigating as potential accomplices.

Unanswered Questions and Societal Reflection

Although Sararat faces 11 counts of first-degree murder, she denies all charges and claims to have mental health issues. Under Thai law, pregnant women cannot be executed. The death penalty can be postponed for up to three years after childbirth, and if the child is still alive after three years, the sentence is automatically commuted to life imprisonment. The baby Sararat carries has become her "get-out-of-death-free card."

This case has cast a long, dark shadow over Thai society, creating a climate of fear and shattering trust. Friends eye each other with suspicion, hesitant to accept even a simple drink or snack from one another. This single serial killer, through her actions, has destroyed the happiness of countless families and eroded the fundamental trust between people.

Sararat might just be the tip of the iceberg. The ease with which cyanide can be obtained and the loopholes in its regulation, coupled with Thailand's growing problem of personal and household debt and a distorted view of money fueled by consumerism, create fertile ground for such extreme crimes. If these deeper societal issues remain unaddressed, will there be a second, a third Sararat in the future? The question is deeply unsettling and demands profound reflection from the entire society. For the victims whose lives she brutally stole, true justice may remain agonizingly elusive.