Maneenetr Charoenngao, 40, was killed at the scene when her neck hit the hanging cable, almost decapitating her.
Muang Khon Kaen deputy inspector Pol Capt Singha Hong-on said it was a small, sharp, fibre-optic cable insulated with tough-type black plastic.
He said police were still checking what caused the cable to slip out of the power cable and hang down.
The accident happened at 5pm on Wednesday in front of Khon Kaen Nakhon School.
Police checked security cameras at the school and saw a 10-wheel truck was driving past and a worker on the back bent his head to avoid the cable.
Maneenetr rode her motorcycle in the opposite direction at the same time and her neck was stuck by the cable, sending her and her motorcycle crashing to the floor.
Singha said police were checking with the provincial electricity authority as to which company owned the cable.
Her eldest daughter, Kanokwan Panyapim, said her family would fight until the end to find the responsible agency because her mother was the main breadwinner for the family.