The poles fell like dominoes on either side of Phuttaraksa Road for a kilometre and half, some landing on two pickup trucks and a six-wheeler.
Police found the CPAC cement truck parked about 500 metres from the damaged cars. The driver, Worrawut Phanitchkul, 25, has been taken in for interrogation and will face legal action.
A wide area in the district was still plunged in darkness as of press time, though the Metropolitan Electricity Authority reckoned electricity would be restored by midnight yesterday.
A passer-by was seriously injured from electrocution, while an old woman sustained injuries when she fainted. They are both being treated at the Bang Na General Hospital.
The road is open to traffic.