Michael Turner, a spokesman for the U.S. Embassy in Bangkok, confirmed the actor's death. Citing unnamed police officials, the Nation newspaper reported Carradine was found dead this morning by a chamber maid at the Park Nai Lert Hotel, where he was staying while shooting his latest film, "Stretch."
Carradine was reportedly found naked in the room's closet hanging from a rope, possibly from the curtains, according to the Nation and police.
"He was found hanging by a rope in the room's closet," Lt. Colonel Pirom Jantrapirom of the Lumpini police station in Bangkok told Reuters.
Police have yet to determine if Carradine died today or Wednesday, according to the U.S. Embassy.
"Yes, I can confirm that Mr. Carradine has passed away here in Bangkok," Turner told The Associated Press today. "We send our heartfelt condolences to his family and his loved ones. It's still under investigation, but it looks like Mr. Carradine passed away either late last night or early this morning. The embassy was informed about it today."
His body, police said, was to be autopsied.
Carradine did not show up for a scheduled dinner Wednesday evening, according to the Nation.
Carradine's friends were shocked to learn of the veteran actor's death.
"David was one of the first actors I ever worked with when I started my career and the closest person to a brother that I ever had in my life," said actor Michael Madsen, who worked with Carradine on "Kill Bill" and in the upcoming "Six Days in Paradise."
"It is shocking to me that he is no longer with us. I had been thinking about calling him for the last several days and advise anybody who has been thinking about reaching out to a loved one to do so. I have so many great memories of David that I wouldn't even know where to begin ... He has a very special place in my heart," Madsen said.
Carradine was perhaps best known for his role as Caine, a Chinese martial-arts master wandering the American West in the 1970s television series "Kung Fu." Though he had starred in more than 100 films, his career was most recently revived in Quentin Tarantino's "Kill Bill" (2003) and "Kill Bill II" (2004) in which he played a steely assassin.
The actor spoke openly about his earlier abuse of drugs and alcohol but had reportedly remained sober for several years.
"I didn't get into drinking till I was in my 40s, and by that time I had stepped away from the rest of drugs," he told the Irish Times in 2004.
"There was only a period of a few years when I was drinking too much. I had a friend who was a mentor, and he suddenly said, 'I've never seen you abuse a substance before.' I said, 'Am I doing that now?' And I was. That was spring of 1996. I like to think that I stopped drinking on St. Patrick's Day, but it was actually a month later," he told the paper.
Born in 1936 in Hollywood, Calif., Carradine came from a showbiz family. His father was actor John Carradine, and his brother was actor Keith Carradine.
Of primarily Irish ancestry, Carradine's ambiguous features landed him a lifetime of roles playing a range of ethnicities, although he was often cast as Chinese.
He most recently starred as Poon Dong, a Chinese mobster, in the action film "Crank: High Voltage."
Additional reporting by ABC News's Dean Praetorius.