Strict measures to control bird flu in Thailand will remain imposed until the end of this year, Vice Minister for Agriculture Charal Trinvuthipong said on Monday.

The control measures will focus on free-range duck-raising farmers who must switch to closed system farming that has been proven to be safer.

About 60 percent of Thailand's duck farmers have registered for the closed system, he said.

Strict measures will also continue to control the spread of bird flu virus carried by migratory birds, he said.

Harsh punitive measures will remain imposed against those who clandestinely transport or sell poultry which have died of unknown cause.

"Campaigns to raise awareness and consciousness of poultry vendors will continue," Charal said.

According to Public Health Minister Pinij Jarusombat, 84 patients in 18 provinces nationwide remain under close monitoring for suspected bird flu infection. No new bird flu patient has been reported in the kingdom since the latest two cases were affirmed last month.