No matter how stifling the heat, every night Sanong Suepthai endures it -- sleeping under two layers of blankets propped up by a pillow placed on her chest, in a house with no air conditioning.
"The pillow helps let a little air in so I don't suffocate. But the smell is unbearable. I have to keep an inhaler in one nostril all the time," she said.
The "smell" that Sanong, a resident of Krok Somboon district in Prachin Buri, refers to is the odour of various chemicals wafting from a nearby factory about 1km from her orchard. The 76-year-old says that during the day, working among the trees in the garden provides some relief, but at night, the stench becomes intolerable. For two years she had to flee to Ubon Ratchathani to live with her younger sister.
"Coming back, I continue to suffer the same problems. Actually, the smell has become even stronger, especially at night," said Sanong.
"I want to speak to someone in power to fix the damage to the air we breathe and to our land. We used to enjoy so much fertility, but now most trees yield fewer fruits. Why is that?"
Sumet Rienpongnam, founder of the Khon Rak Krok Somboon Group, has been campaigning to address pollution in Prachin Buri. He reckoned the crisis escalated further during the Prayut Chan-o-cha government following a military-led coup.
The military regime issued the Order of the National Council for Peace and Order (NCPO Order) 4/2016 that exempted certain types of businesses from the enforcement of urban planning laws for green zones. Thus Prachin Buri, a province once renowned for its pristine nature, organic farming, herbal products and eco-tourism, has since witnessed a mushrooming of factories. As of 2025, there were 1,067 factories across the province.
In particular, Sumet pointed fingers at factories dealing with waste treatment and hazardous waste disposal.
"These waste-sorting factories are the source of soil, water and air pollution because there is no real sorting happening -- they just pile things up. The waste is not only from factories in Prachin Buri itself but also from Rayong or even from abroad. They simply dump it. They may sort some of it, but what remains after sorting becomes a dumpsite," Sumet explained.
Sumet took me to Ban Na Khlong Klang in Khao Mai Kaew, Kabin Buri -- called Pong Chang Thang among locals -- where mounds of gypsum waste were scattered across approximately 200 rai of open land, about 2.3km from Na Khlong Klang School. Sumet estimates the total volume of gypsum to be several million tonnes.
Locals call the mysterious substance "fertiliser gypsum", so called because the factory marketed it as a "gift" several years ago. (Natural gypsum can be used as fertiliser and is found in many Thai provinces.)
"At first, we were happy when they said they'd bring us fertiliser to use for free. When it first arrived, it had no smell," recalled Thongkham (a pseudonym), aged 64. She said villagers eagerly pooled their national ID cards for the "fertiliser" -- one card per pickup truck load. The chunks were quite hard and villagers had to hire excavators to till it into the soil before planting cassava shoots.
Before long, the cassava shoots they had planted began to yellow, rot and die -- hundreds of rai of loss in total.
"It took years for the villagers to rehabilitate the damaged soil -- using animal manure, fallen leaves and other organic matter -- to the point where they could grow small amounts of food," Thongkham said.
They complained to the factory responsible for the waste, asking them to take it away for proper disposal, but if anything, even more waste seemed to be dumped. Her home is less than a kilometre from the pile of the mysterious material.
Thongkham herself suffers from headaches and palpitations and takes medication daily.
"I feel sorry for the children at Na Khlong Klang School who have to endure the stench," she said.
We collected pieces of the 'gypsum' scattered along public roads, dissolved them in water and tested the acidity using litmus paper -- the result was pH 4. Additionally, we obtained documents from a private laboratory hired by the factory to test the 'gypsum', which showed the acidity to be even lower than that. [A neutral pH is 7; acidity starts from zero.]
I spoke on the phone with a staff member at the factory in Ban Bu in Si Maha Phot district. The staff member [who declined to give her name and could not be reached afterwards] claimed that the product of cassava fermentation was citric acid, which could be used in food and cosmetic products for export.
She called the residue from the fermentation process 'gypsum', and claimed it was sent to a cement factory in Saraburi to be made into construction products. I contacted the cement company and its senior executive [who also requested anonymity] said they had received material from the said company but it would be incinerated for disposal, which contradicted what the factory staff had said earlier.
Notably, before 2023, the Department of Industrial Works (DIW) had certified gypsum as a "by-product" of cassava fermentation. But after villagers' repeated complaints to the DIW about the odour from the cassava fermentation process, the DIW conducted an investigation and issued a letter dated June 15, 2023, stating that it was not a safe product but was, in fact, hazardous waste.
Campaigners also obtained a purchase contract for calcium sulphate (gypsum) written in Chinese with Thai translation, bearing the stamps of both companies and signed by their representatives -- between seller and buyer, dated May 30, 2023. Intriguingly, the contract did not specify pertinent details, such as the selling price per tonne.
After years of complaints about pollution from industrial waste-sorting factories, the National Assembly revoked the NCPO order on July 25, 2025, citing its damage to communities and the environment. However, the law has no retroactive effect and cannot revoke licences already issued to factories currently in operation.
Moreover, the government is pushing for Prachin Buri to be incorporated into the Eastern Economic Corridor (EEC) project. Thammasat University has been commissioned to survey and produce a report on how joining the EEC would improve Prachin Buri's economy, boost business and the employment rate.
But Sumet is worried that if this EEC expansion policy succeeds, the pollution problem will only overwhelm his hometown further.
"What chemical contaminants are in the air, water and soil?" he said.
"Can those who have studied this tell us what people in Si Maha Phot are breathing every day -- what is in it, how dangerous it is and which factories are producing it? How many contaminated areas are causing suffering to villagers and where are they? And how will the problems be solved?," Sumet questioned.
"How many millions of cubic metres of water does all the existing industry use, and how many millions of cubic metres of wastewater are discharged? How is the wastewater managed?," he added.
One of the concerns raised by villagers is the quality of water, which is already often discoloured and murky. Villagers are uncertain whether, given the environmental pollution, rainwater might seep into the groundwater system.
"We don't have much money, so we can only afford to buy drinking water. For cooking food and rice, washing dishes, and bathing, we have to use groundwater," said Thongkham.
Last August, the Sut Soi Team, together with the DIW, armed with a search warrant from Kabin Buri Provincial Court, inspected Waste to Energy Company in Lat Takian, an area straddling Si Maha Phot and Kabin Buri districts. The factory was found to have committed multiple violations and ordered to suspend its operation. But in October, a new official came and allowed the factory to reopen.
Dawan Chanhatsadi, a senior member of the Earth Recovery Foundation, who accompanied the Sut Soi Team, revealed that the factory held two types of permits -- 105 for non-hazardous waste disposal and 106 for recycling industrial waste -- yet had no machinery for recycling.
"It has been accepting hazardous waste -- so where has all of it gone?" Dawan asked.
"Have all issues been resolved? What happened to the water that was overflowing from the landfill pit? What has been reduced? And does the factory now have the machinery?"
Sumet raised the same question: "For years everything has gotten worse. The waste piles grow larger every year -- tens of millions of tonnes -- and the smell is worse than ever. Today, the minister came for a visit, praised the company for making improvements and for their cooperation, and then simply left."
