At least 29 people were killed and 23 injured when a passenger bus skidded off a highway and into a 50-metre ravine in northern Thailand, dpa cited police as saying Tuesday. Most of the casualties were elderly residents of Tak province, 400 kilometres north of Bangkok, on an educational tour to Laos in a convoy of four buses and 200 passengers. The accident happened at 8:40 pm Monday (1340 GMT), about an hour after the convoy left the town of Mae Sot on the Myanmar border, said Police Captain Sitichai Panyanong from Tak's sub-district of Nae Tor. He said the ill-fated bus was the last in the convoy and was "speeding down a hill when the driver lost control at a curve." The driver was among the injured, he said.