And in those earlier cases, resistance also started in Western Cambodia, and in a similar way.
No-one is sure why this area seems to have become a nursery for anti-malaria drug resistance.
One factor could be the inappropriate use of drugs, related to a lack of medical supervision.
The public health system is weak. Government clinics often run out of drugs or may be closed when patients want access to them.
Sure, I'm biased after working for an American pharmaceutical firm and dealing with the obsessive compulsive regieme of the FDA. [after being in the hospital and staring at a bag of solution being pumped straight into my body - that will make you change your mind about how good it is for document control and quality assurance.] But really - this is beyond the pale of people here:
All pharmacies are supposed to be licensed. But the stallholder told me he didn't have a licence. He'd applied for one, he said, but the paperwork had never been processed.
Many others running pharmacies, he said, were in the same position.
I watched him and his wife make up their own packets of drugs on the glass-topped counter, shaking a variety of coloured tablets into unlabelled plastic bags.