"Kung Fu" and "Kill Bill" star Carradine, 72, was in Bangkok to shoot his latest movie, Stretch, and stayed at the Nai Lert Park Hotel on Wireless Road at Suite Room 352 since June 2.
Thai police believed he committed suicide.
The film crew were aware of his absence when they went to dine out at a restaurant on Sathorn Road on June 3.
Carradine did not show up at the dinner and the team could not reach him. They assumed that he took a rest because of his age.
It was the hotel's maid who opened his suite on Thursday at 10 am only to find Carradine in a closet. He was described as behind half naked.
Police investigation showed that he hung himself with a rope, the kind used with curtains.
Police said he was dead for not less than 12 hours and found no sign of fighting and assaults.
His personal manager, Chuck Binder, told BBC that the news was "shocking", adding: "He was full of life, always wanting to work... a great person."
Aside from Quentin Tarantino's two-part "Kill Bill" in 2003 and 2004, Carradine was perhaps best known for his role as the fugitive half-Chinese Shaolin monk Kwai Chang Caine in the 1970s easternwestern TV drama "Kung Fu". He also starred in Martin Scorsese's "Boxcar Bertha" in 1972, portrayed folksinger Woody Guthrie in "Bound for Glory" in 1976, acted in Ingmar Bergman's "The Serpent's Egg" in 1977 and co-starred with half brothers Keith Carradine and Robert Carradine in the 1980 western "The Long Riders".
His father was the noted actor John Carradine.
In Thai cinemas, Carradine was recently seen as a martial arts guru in the Rob Schneider comedy "Big Stan" and as a perverted elderly Chinese mobster in "Crank: High Voltage" starring Jason Statham.
