An American tourist who claimed to be stranded in Thailand due to COVID-19 restrictions was found dead in his rented room.

James Thomas Paull, 52, from Washington, D.C., was found half-naked lying face down on his bed in Krabi province on January 20.

The tourist arrived in March last year and rented the room after telling staff that lockdown restrictions prevented him from returning to his home country.

As his rental payment was overdue, the staff went to his room to check with him. They became concerned after a foul smell seemed to come from his room.

After knocking on the door several times, they decided to forcefully open the door.

They were shocked upon finding that the man's body had started to decompose on his bed.

They called the emergency services for help who recorded the crime scene before James was taken to Surat Thani Hospital for a post-mortem examination.

One of the staff said the tourist was last seen three days before he was found dead, using his computer on the lobby.

She said: "He seemed fine three days ago, we also did not hear anything suspicious from his room so we were shocked when he was found dead.

"He likes to have beer inside his room and sometimes returns drunk but he didn't give us trouble."

One of the police officers who responded said they will reach out to a Malaysian girlfriend who was identified to visit the apartment to see James.

The officer said: "We will interview everyone who was in contact with him to find out what happened including his girlfriend."

As the man was a heavy drinker, the officer added that the cause of death may have been due to an underlying disease as there were no signs of struggle in his room.

However, the cause of death will be determined after the autopsy while investigations are ongoing.

Thailand stopped international tourists from arriving on March 22 last year.

Flights out of the country have been allowed so it is unclear why James was unable to return home.