A member of the study, Robert Amato, said, "We found transgressions moving, replacing local moralists, and becoming the Dominant strain in Vietnam, Laos and north-eastern Thailand."
The drug combination known as DHA-PPQ was initially effective against parasites, before doctors saw signs of resistance in 2013.
A recent study of the failure rates of DHA-PPQ shows that they have now reached 53% in South-West Vietnam, and as high as 87% in northeastern Thailand.
Meanwhile, Olivo Miotto of Oxford warned of the "terrible prospect" of parasites that spread to Africa, where most cases of malaria fall.
Resistance similar to the old type of major malaria drug, chloroquine, contributed to millions of deaths across Africa in the 1980s.
Malaria kills more than 400,000 people a year, mostly children in Africa.
More than 200 million people are infected with the P. falciparum parasite, which is responsible for nine of 10 malaria deaths in Malaria.