By Jonathan Head
BBC News, Bangkok
One of the world's biggest pharmaceutical companies has announced it will stop licensing any new drugs it develops for sale in Thailand.
Kaletra is a widely-used anti-retroviral drug
US-based Abbott Laboratories said it was responding to the Thai government's decision to break the patent on the anti-HIV/Aids drug Kaletra.
Thailand has announced it will either make or import cheap generic versions of three patented drugs.
The health ministry said it wanted to cut the cost of healthcare.
The decision is the boldest challenge yet by a developing country to the global pharmaceutical industry.
Under World Trade Organization rules, poorer countries can issue what are called compulsory licences to make cheaper, generic versions of branded drugs if they face a health crisis.
The big multi-national companies have already accepted this in the case of basic anti-retroviral drugs in order to cut the death toll from HIV/Aids.
But they argue Thailand has gone too far in issuing compulsory licences for two newer HIV treatments and a heart drug.
They say this amounts to theft of their intellectual property, and that Thailand should have negotiated first.
One of the companies affected, Abbott Laboratories, has now struck back, by refusing to sell any new drugs it develops in Thailand.
The Thai health ministry argues that the companies' prices are too high, putting an impossible burden on the government, which is one of the few in the developing world to offer universal, free healthcare.
Thailand's action is being applauded by health campaigners.
Even the US, which usually supports patent protection, says Thailand is within its legal rights to take such action.
But if other big drug companies follow Abbott's example, patients in Thailand could find themselves deprived of vital treatments in the future.