The 56-year-old man was among six people tested for bird flu, of whom two were confirmed to have caught the virus.
"The man died of pneumonia this evening," Charal Trinwuthipong, director-general of the Department of Disease Control, told reporters on Friday.
Earlier on Friday, the European Union announced it is set to ban imports of Thai chicken after Thailand confirmed two cases of humans infected with the deadly bird flu ravaging Asian countries.
EU health commissioner David Byrne "has suggested to his colleagues (on the EU executive) to stop imports of poultry and poultry products from Thailand to the European Union", his spokeswoman said in Brussels.
The ban would be announced shortly, she said.
After weeks of denials, Thailand admitted on Friday that bird flu had infected humans and chickens in the kingdom, and ordered a complete halt to its billion-dollar poultry export business.
The EU is Thailand's second-biggest export market for poultry after Japan. It is the only Asian country to export poultry to the EU.
Shockwaves in Thailand
"Any (Thai) chicken with a certificate dating it after January 1 will be impounded"
A French farm ministry official
Japan announced on Thursday a ban on imports of Thai chicken in response to Bangkok's first reported case of bird flu.
The announcement sent shockwaves around the Thai industry which exported 540,000 tonnes of chicken last year, half of which - 270,000 tonnes - went to Japan while the EU took 166,000 tonnes.
The H5N1 strain of avian influenza has already killed at least five people in Vietnam and 17 other people are believed to be infected. Bird flu has also been reported in Japan and South Korea.
Millions of chickens have been culled across Asia in a bid to
curb the outbreak.
The French move
Earlier on Friday, France decided to impound imports of fresh chicken from Thailand dated after 1 January over the flu outbreak, a farm ministry official said in Paris on Friday.
Bird flu has already killed five
people and infected 17
"Any chicken with a certificate dating it after 1 January will be impounded," the official said, adding that it did not concern meat that was already in supermarkets because that would have been dated before 1 January.
In Thailand, shares in agricultural firms plummeted and analysts warned the lucrative tourism industry could be harmed. Prime Minister Thaksin Shinawatra appealed for calm and said panic would not grip the stock exchange.
"It is a short-term effect as the bourse is sensitive to psychological factors. The hard hit sector will be the poultry industry," said the premier who on Tuesday ate chicken in a stunt to boost confidence in the industry.