The National Human Rights Commission has condemned businesses that require job applicants to be tested for HIV, saying the move is a "clear violation of human rights".
The NHRC said requiring people to take a blood test could adversely affect people who do this, plus their families, both economically and socially.
The agency was responding to complaints from the many people who say they were asked to undergo a test for HIV before they could be hired.
The problem is people found to be HIV-positive are often stigmatised and discriminated against, the office said.
It has called on relevant agencies to stop the practice.
Tairjing Siriphanich, a National Human Rights Commissioner, said there was no reason for businesses to test prospective employees for HIV, as the virus had no affect on how someone performed professionally.
"HIV is not a scary thing because it can be treated and controlled through medication, almost like someone who has diabetes," he said.
"Sometimes those with HIV are not even sick but once they are known to possess the virus they will be stigmatised and rejected by society."
Tairjing said blood tests for HIV at workplaces could be categorised into two groups.
Firstly, some businesses require blood results prior to hiring job applicants and people found to be HIV-positive tend to be rejected.
Secondly, there are employees who are asked to undergo a blood test. In at least one case, an employee was fired after testing positive for HIV.
Tairjing said even employees who fight back and win reinstatement are usually transferred because of the stigma.
He said people with HIV even face discrimination from family members, such as being told to eat at a separate table or being kicked out of the house.
He questioned the need for HIV blood tests given other viruses such as hepatitis B were "more deadly".
The blood-test requirement can also cause an unnecessary financial burden on job applicants.
"One of the many reasons why people refuse to take blood tests is the cost," he said. "Why is it the job applicant's responsibility to pay for the blood test."
Job applicants asked to be tested for HIV can file a complaint with the NHRC by calling its 1377 hotline or via email@example.com.