A schoolgirl was tragically electrocuted while trying to charge her phone with a frayed extension cable.

Rattanawadee Poontawee, 12, was found dead at her house in Nakhon Nayok province, Thailand, on February 13 after grabbing the phone charger which was still plugged into the extension socket.

Her grandmother, Chaweewan Poontawee, 58, was in another room when she heard a loud bang 'like someone falling down'.

When the older woman went to check, she was greeted with a horrifying sight - her granddaughter lay on the floor twitching after touching an exposed portion of the electricity cable's wire, which was attached to her phone.

Chaweewan ran to switch off the circuit breaker at the main point on the wall before checking on the youngster who had stopped moving.

She called the emergency services but the girl had died before she could be rushed to a hospital.

A distraught Chaweewan said 'I did not see when it happened. I think she was shocked because she picked up the peeled part of the wire.'

Police collected evidence from the scene while the bereaved family prepare for Rattanawadee's funeral. They are not investigating further.

Last week, a welder in Bangkok died in his bed after being electrocuted while charging his phone. He had plugged his power strip directly into a socket without using the proper adapter.