Chawanlak Phattatrakul, 24, shared her experience on Facebook, which drew the attention of netizens before police stepped in to investigate.
She said she was on a motorbike with her mother when two men on another motorbike approached them, and the man riding pillion pulled out a knife demanding they stop.
However, she said, her mother sped off screaming for help and the offenders fled.
People in the province are concerned about their safety as this is the third time this month that armed men have attacked people in public.
On December 5, a man under the influence of drugs killed two people and injured six, and then again on December 12, a man attacked a Grab employee with a knife on a busy street.