Theerasak Longji, 26, was convicted for the brutal killing of a 17-year-old boy in Trang.
He stabbed his victim 24 times in a frenzied attack on July 17, 2012, before making off with his mobile phone and money.
Theerasak was convicted of the crime and his conviction was upheld by the Appeal Court and the Supreme Court.
The death sentence was carried out in line with regulations and the Criminal Code, Col Naras said.
Theerasak was the seventh convict to be executed by lethal injection since it was introduced in 2003, replacing execution by firing squad.
Col Naras said 326 convicts have now been put to death since modern-day executions were introduced in 1935.
A total of 319 people faced a firing squad which was officially abolished on Dec 11, 2003.
The first convict to receive a lethal injection came the next day.
Theerasak’s execution was the first death sentence to be carried out in Thailand since August, 2009, when two drug traffickers were executed simultaneously.
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