The accident took place at 5am at kilometre marker 2 on Road 41 and police suspect the driver fell asleep while driving the Siam Transport Co inter-provincial bus from Bangkok to the commercial district of Songkhla province.
Chaithawa Siwbuan, head of the Disaster Prevention and Mitigation office in Chumphon, said 13 of the injured were able to go home after receiving treatment while the rest were taken to Chumphon Hospital.
The accident came after the Transport Ministry's promise for better safety for passengers following an accident that killed 29 people and critically injured four when a bus from Chiang Rai to Khon Kaen province plunged into a deep ravine in Phetchabun province on Thursday night.
Meanwhile, a vehicle collision at a road curve in Buri Ram's Satuk district on Sunday killed four and injured three, one of whom is a young child, police said.
Anuchit Chaodong, an officer at Satuk police station, said a bronze Mitsubishi Lancer with one passenger was in the wrong lane when it crashed into a white Suzuki car with five people inside.
Sathit Charoenrat, the driver of the sedan, 40, was found dead inside his vehicle. Adisorn Rakpla, 25, the other driver, Katchanee Nongharng, 47, Thonporn Kitjak, 38, a 15-year-old teen and a 3-year-old were rushed to Satuek Hospital.
Mr Adisorn later succumbed to his injuries. Information on the other dead was not available.
A preliminary investigation revealed that the group in the white Suzuki were going to visit relatives in Kalasin province when at a curve, the bronze car that was going the opposite way drove into their lane as it attempt to overtake another vehicle leading to the collision.
Pol Lt Anuchit said the accident caused heavy traffic congestion. Authorities took about an hour to clear the road.
Despite promises made by the police to implement strict traffic regulations during the 2013 New Year period, the number of fatalities and injuries from road accidents continues to soar.
Traffic accidents on Dec 28, the second day of the "seven dangerous days of 2013 New Year" claimed the lives of 47 people and injured 486, based on reports by the Disaster Prevention and Mitigation Department. That increased the road toll for the first two days to 86 killed and 885 injured from 866 accidents.