The sister of murdered backpacker Hannah Witheridge has warned that Thailand is a “dangerous trap”, suggesting her sister’s killer walks free and slamming the Thai police and government for mistreating her bereaved family. In a long Facebook post, Laura Witheridge said “the vast majority of the Thai police are corrupt” and the investigation that led to the death sentence last month for two Burmese men was “bungled”.

She also hinted she believed Thai, not Burmese, nationals killed her sister on Koh Tao island and she received death threats throughout the trial, including one saying the killers had completed only “half the job”. “What if I told you that I am now frightened of my own shadow?” she wrote.

Witheridge said she was compelled to write the public post after an “ignorant (Facebook) comment someone had made about how Thailand is the most beautiful place in the world”. “Aesthetically, on a postcard or photograph, maybe,” she said. “Aesthetic beauty can lure you into a very dangerous trap.”

When her family visited in 2014, Witheridge said, Thai police offered to provide them with an official update at their headquarters but “200 journalists were allowed into the room and we were ambushed by this mob of hungry journalists shoving cameras in our faces”. She added: “The Thai police chief had no intentions of giving us an update … after all, the bungled investigation meant he had nothing to tell us. The invitation was merely an opportunity for the press to take photographs of our family.”

The family was later “absolutely appalled” when “the Thais offered us ‘compensation’”.