People could sue red shirts if they violate their rights, National Human Rights Commission chairwoman Amara Pongsapich said Monday.
They could also lodge a complaint against local police for failing to carry out their duty to protect people.
In the previous weeks, the red shirts set up checkpoints to block and search vehicles in many provinces. In many cases, they assaulted people who refused the search.
"Police cannot allow any unauthorised person to conduct a search or intimidate others," said Amara.
At the same seminar, Foundation for Consumers secretary general Saree Ongsomwang urged police to protect people.
"If the police do nothing, hatred among people with different opinions will grow," she said.
She also urged the redshirt demonstrators to stop violating the rights of other people.