A newborn baby was rescued after being abandoned inside a backpack and left by the roadside in Thailand.

Footage shows a rider wearing a black top and shorts dismounting her motorcycle and appearing to place a bag on the roadside along a busy highway in Samut Prakan on July 16.

The following day, resident Sak Chinnabut recalled that while collecting bottles for sale, he had walked in front of a parked truck on a bridge when he noticed a slightly open bag lying on the road surface.

Curious as to what might be inside, he looked closer and was shocked to see a baby's head.

He immediately called for help, retrieved the bag, and contacted the authorities.

Paramedics and police officers from Bang Phli district station arrived at the house where residents had taken the infant.

They found the baby was female, with her umbilical cord already cut, and she appeared to be in good health.

The child was taken to Chakri Naruebodindra Medical Institute for a medical check-up and temporary care while awaiting transfer to the appropriate child welfare agency.

Police Major Santirat Ngernman said: 'Investigators are checking security cameras near the scene, and we've also deployed a team to track down the child's mother or the person responsible for abandoning her.

'We are cross-checking hospital birth records to support the investigation and pursue legal action.'

Officials added that the area had experienced heavy rainfall overnight, and the baby had remained in the backpack until she was discovered and rescued the next day.