This is the shocking moment a grandmother fell down the stairs after being startled by an unleashed pet dog at an apartment in Thailand.

Chalao Chansawang, 76, was walking up the steps to return to her room when the pet pit bull suddenly charged at her at the Pisarn Condominium in Samut Prakan.

CCTV footage shows the large canine, which had broken free from its leash, bounding down the corridor before lunging at the hapless pensioner on July 17.

The woman lost her balance when the dog barked at her, falling backward and tumbling down the stairwell from shock. She was rushed to Samut Prakan Hospital where she received six stitches for a head wound and complained of hip and rib pain.

Despite her injuries, the elderly tenant said she would not press charges or demand compensation from the dog's owner 'because she felt sorry for him'.

She said: 'The dog owner took full responsibility and cared for me throughout my hospital stay. He even bowed down, admitted his fault, and sincerely apologised.

'I didn't press charges or ask for compensation because I saw that he tried his best to take care of me. No one wanted this to happen, but he handled everything with sincerity.'

The grandmother added she was acquainted with the man as he was also a long-time resident at the apartment.

Thailand is notoriously unregulated over pets and there are no laws preventing people from keeping dangerous dogs. Despite numerous fatal pit bull attacks reported in the news, stubborn locals continue to keep the rabid animals as companions.