For generations, the secrets of "Kru Khmer" traditional remedies have been passed down by word of mouth -- often from father to son -- with each expert tweaking the methods along the way.
But in an attempt to freshen up the ancient art and better regulate the industry, Cambodia's Ministry of Health has opened a traditional medicine school, with funds from a Japanese foundation.
Cambodia is home to thousands of Kru Khmer practitioners -- medical plant experts whose mysterious concoctions of roots, barks and leaves are used to heal common ailments.
The school, which opened in 2009, has trained some 345 Kru Khmer so far, with a particular focus on hygiene and anatomy.
"It's good to have training like this because it teaches us correct, safe methods," said Kraing Dhein, a student at the school.
A certain kind of tree bark is said to help breast-feeding women produce enough milk, while the pungent durian fruit is well-known as a treatment for rheumatism.
Other remedies are potentially dangerous -- in the worst case, powerful homemade rice wine is known to have been recommended to pregnant women.
"This training is more professional than what students learn from their ancestors," said Kong Sokdina, project manager for CatMO, a traditional medicine organisation that manages the courses.
"They are taught many subjects, such as the ethical code of treatment... they wouldn't know otherwise."
During the five months of training, students are taken on regular field trips to study local varieties of plants and learn about their natural healing properties -- such as those that can act as antibiotics or have antiseptic qualities.
The final trip on the course is to southern Kampot province, home to many unique plant species.
"We can find roots that no longer exist elsewhere," said professor Ky Bouhang, chair of the Cambodian Traditional Healers Association.
Some 80 percent of Cambodia's population live in rural areas, often in villages with no doctors, let alone a hospital.
Even where local healthcare is available, many villagers cannot afford professional medical care.
Traditional healers offer a cheaper alternative -- and business is prosperous.
On the outskirts of Phnom Penh's Orussey Market, many Kru Khmer man tables heaped high with dried plants and animal parts, roots, barks and other traditional treatments.
Tauch Sreythoeun opened her stall at Orussey soon after she finished training.
"Some (customers) want plants to help reduce fever, for example, so I mix them a treatment from several roots," she told AFP.
Patients usually seek out a Kru Khmer for help with minor gripes, such as stomach aches and exhaustion, which do not demand the attention -- and expense -- of a proper doctor.
"Traditional medicine can help treat the poorest people because people (living) in the country do not have enough money to go to the hospital or see a doctor," said Soung Kimsath, still a Kru Khmer student.
But some adherents claim the discipline is so powerful that it can replace modern medicine entirely.
Pov Rany has regularly consulted traditional healers ever since she discovered she had a cyst in her chest.
"I believe in traditional medicine, I think it is effective and good for my health," she said.
"I don't use modern medicine because drugs contain chemical substances and counterfeit products."
Some doctors warn about the dangers of relying solely on traditional healers -- especially for serious illnesses.
But in Cambodia, the pull of traditional medicine is strong.
Many see it as tried and trusted ancient wisdom in contrast to the country's myriad local pharmacies, which dole out expensive and often counterfeit Western medicines, with no proper advice or prescription.
The most obscure power of the healers pertains to the spirits. Many Cambodians believe Kru Khmer have the capacity to literally blow bad spirits out of the body.
"I cured a woman who had shingles with my magic breath," said Ky Bouhang.
"Today, she can work again in her farm while no other treatment had been a success." - July 8, 2013.