Tests confirm that the boy has the virus. He is, however, expected to make a full recovery.
Of the 21 people who have contracted bird flu in Thailand, 13 have died.
So far, all the humans killed are believed to have contracted the virus through contact with infected birds.
Several fighting cocks and a chicken kept in the same house as the boy died soon after his flu symptoms were reported.
Thailand's director general of disease control, Thawat Sunthrajarn, says that the baby boy "is recovering and is almost back to normal".
