Drug-resistant bacterial infections are increasing in Thailand because of poor policy and an absence of regulation and are killing more than 19,000 people a year compared with 23,000 a year in the United States, researchers warned on Wednesday.

The problem, largely caused by the over-use of antibiotics among people and livestock, could hit Thailand's profitable medical-tourism sector.

"Drug resistant bacteria is spreading in Thailand and, very likely, in all low and middle income countries," Direk Limmathurotsakul, lead author of a study by Britain's Oxford University and Mahidol University in Thailand, told Reuters.

The researchers estimated that drug-resistant bacterial infections killed 19,122 people in Thailand in 2010.

When adjusted for population, the problem was much more severe than in the United States and the European Union, where about 25,000 people die a year from such infections.

People in Thailand can buy antibiotics over the counter and many take them "without really needing them", fueling bacterial resistance, Direk said.

The excessive use of anti-bacterial drugs by farmers also "generates antimicrobial resistant bacteria in the environment".

"The impact of drug-resistant bacterial infections is already considerable - and getting worse," said study co-author Nick Day of Oxford University.

"If it's not to overwhelm ... the world's economic, health and life expectancy gains, we need to take drug resistance seriously and invest heavily in its defeat - now," he said.

About 2.5 million foreigners visit Thailand every year for health services and Direk said that while private hospitals "have enough resources" to address the situation now, the sector could be affected in future if authorities did not take the fight against drug-resistant bacteria seriously.

"Private hospitals have to admit patients from all over the world, who could have already had drug-resistant bacteria with them," he said.

"All sectors and all countries need to tackle the problems together as this is a global problem."