The incident early today close to a protest site will hasten fears that the country's political crisis could lead to a serious outbreak of violence.
The Erawan medical centre said a 31-year man was killed with wounds to his torso.
Protesters are seeking to topple prime minister Yingluck Shinawatra ahead of elections scheduled for February 2.
Clashes on Thursday killed two people in the capital as protesters sought to disrupt preparations for the polls, which surveys suggest Ms Yingluk will win easily.
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