The Public Health Ministry has warned that the incidence of influenza is spreading rapidly, with four provinces in the northeast region the hardest hit.
Public Health Minister Somsak Thepsutin said there had been a big jump in infections this month. Health officials were speeding up the suppy of vaccines to sensitive groups, particularly children and senior citizens.
There were 7,819 cases of influenza this year as of Jan 25. However, by Saturday, Feb 15, total infections this year had leapt to 99,057, with nine fatalities.
Most cases were found at schools, and children aged 5-9 years were the most vulnerable group, according to the ministry. Nakhon Ratchasima, Surin, Buri Ram and Chaiyaphum were the worst affected, with about 6,938 patients combined.
Mr Somsak said people showing symptoms that could be flu should stay home, to prevent spreading the virus.
The incidence of influenza in Thailand has risen steadily from about 472,000 cases in 2023 to 668,000 last year, according to the Department of Disease Control.
The present trend suggests the figures this year will surpass last year's, when 47,000 cases were reported from Jan 1-Feb 3, compared with almost 100,000 cases so far this year.
H1N1 is the main virus strain active in Thailand at present, according to the health ministry.
Yong Poovorawan, a virologist at the Chulalongkorn University faculty of medicine, posted an advisory on Facebook on Feb 9 saying that travellers to countries in the northern hemisphere should get a flu shot at least two weeks before going abroad.
But he has also called for calm, saying that the flu is seasonal and Thailand does not have the same variant that is hitting Japan.
"Influenza is seasonal. It spreads in the cold season in the northern and southern hemispheres," Dr Yong wrote.
The situation in Japan caught public attention in Thailand when famous Taiwanese actress Barbie "Big S" Hsu died after catching the flu early this month while in Japan. She was popular in Thailand for her role in Meteor Garden, a romance series.