In a Facebook post, Tharathip Samart said the incident happened on Friday as she walked from the second-floor car park to the entrance of the store in Bangkae, western Bangkok.
She declined to name the mall, only saying it was a well-known department store, but posted photos of the dead snake and her swollen left foot as evidence.
She said that after being bitten she had to kill the snake as there was no security guard around to help.
Tharathip said she reported the incident to officials at the store, but they just asked her where she could receive free medical treatment. The store then took her to hospital but did not treat the incident as an emergency and failed to call an ambulance, she added.
Store officials then left her at the hospital without taking care of her medical expenses, she complained.
Tharathip said she called the department store but was told by an official there that it did not own the snake and therefore would not take responsibility for the incident.
After she threatened to post details of the incident on social media unless the store took responsibility, the official replied that she could do anything she liked but the store would not take responsibility as it did not raise or own the snake.
She said the official added that the senior staff member who could make a decision had not yet returned from the long holiday.
Meanwhile, well-known lawyer Decha Kittiwitthayanan said the department store could not deny responsibility as the incident happened inside its compound.