Carradine, 73, was working on a new film in Thailand. Initial reports suggested suicide but Carradine's agent confirmed to Bangkok's WABC network that he believed Carradine had died of natural causes.
Carradine played Kwai Chang Caine in smash hit 1970s TV series Kung Fu, and regained his iconic glory recently when he played titular villain Bill in Quentin Tarantino's Kill Bill movies.
Carradine was last seen in this year's release, Crank 2: High Voltage, where he played Poon Dong.
Son of prominent actor John Carradine, David has had over 200 movies and television appearances, and his best work involves master directors like Tarantino, Martin Scorsese and Ingmar Bergman.
He is survived by his wife, Annie Carradine.