A Canadian tourist, shot while riding in a pickup truck in northern Thailand, may have been hit by a stray bullet from a hunter, police said on Thursday.

Erik Griffioen, a university lecturer from Ontario, was on trekking holiday with his wife when he was hit by a .22 bullet on Wednesday in the northern city of Chiang Mai, a popular tourist destination.

It was the fourth shooting involving Canadians this year.

"The bullet that hit him might have come from a bird hunter or someone who accidentally fired a gun," Police Lieutenant Colonel Thwatchai Punpigul said.

He said the truck had passed by a forested area when Griffioen was shot in the back. He was recovering in hospital after an operation to remove the bullet.

"There is no motive to hurt him because he had no personal conflict with anybody," Thwatchai said.

Some 150,000 Canadians visited Thailand in 2006, among the more than 13 million foreigners who arrived in the Southeast Asian nation that year.

This latest shooting has raised questions in the Canadian media about safety in a country best known as the "Land of Smiles."

Last week, Canadian oil worker Dale Henry, 47, was shot dead in his home in the southern province of Ranong. Police have charged his Thai wife, her boyfriend and a gunman with murder.