Bangkok - A Thai tour bus taking university students on a field trip overturned on a road ramp Friday, killing 22 people and injuring 27 others, police said.

The driver apparently lost control of the vehicle about 3 am when it was coming down a steep hill in Nadi district, Prachinburi province, 140 kilometres north-east of Bangkok, and it overturned after crashing into a road guard up a dirt ramp.

The driver died in the crash along with 18 male and three female students from Kaset Techno Khon Kaen University.

Prachinburi police chief Major General Sanchai Chaiamporn said authorities were investigating the cause of the accident.

Bangkok - Top leaders of an anti-government movement that has occupied Thailand's seat of government since August surrendered Friday to police, news reports said, a day after treason charges were dropped against them.

The leaders of the People's Alliance for Democracy (PAD) still face charges of resisting arrest and gathering illegally for the actions of their group, which was involved in deadly clashes with police this week and seized Government House August 26 in its five months of demonstrations aimed at toppling the government.

The treason charges dropped Thursday by Thailand's Appeals Court carried a maximum sentence of death. Under the lesser charges, the nine PAD leaders now face a maximum sentence of seven years in prison if convicted.

Bangkok - Former deputy prime minister General Chavalit Yongchaiyudh has called for a military coup as the only means of solving Thailand's political stalemate, the Bangkok Post reported Friday.

"There is no other way out," said Chavalit, in an exclusive interview with the Bangkok Post, an English-language daily.

"I see a putsch. After the military steps in, power should immediately be returned to the people and an interim government can be formed in which every party takes part," he said.

Bangkok - A Thai tour bus taking university students on a field trip overturned into a ditch Friday, killing at least 22 passengers and injuring about 30 others, police said.

The driver lost control of the vehicle when navigating a steep curve in Nadi district, Prachinburi province, 140 kilometres northeast of Bangkok, said senior sergeant Thiradej Virakul of Wang Daeng police station.

"We suspect the brakes didn't work," Thiradej told Deutsche Presse-Agentur dpa.

Bangkok  - Embattled Thai Prime Minister Somchai Wongsawak will visit Laos, Cambodia and Myanmar next week despite problems at home, foreign ministry sources said Thursday.

Somchai, who was appointed premier on September 25, will visit Laos on Sunday, Cambodia on Monday and Myanmar on Wednesday, the Thai Foreign Ministry announced.

He has scheduled similar one-day visits to Singapore and Indonesia in the near future, said a ministry official.

Somchai has had a tempestuous first week in office.

Bangkok - Forensic evidence on casualties of Tuesday's bloody showdown between police and anti-government protestors in Bangkok suggest that deadlier weapons than teargas were used in the clash that left two dead and more than 400 injured, doctors said Thursday.

Angkhana Radabpanyawoot, 25, one of the casualties in Tuesday's clash, was killed by an explosive, not a teargas canister, according to Dr Vichan Peonim, the head of Ramathibodi Hospital's forensic department.