"We have never certified any product that has the ability to reduce fat in any specific area of the body," he said.
He spoke after several internet idols apparently promoted the products online.
The substances advertised online for injections refer to two categories of drugs. The first are steroids, which are used to treat swelling. Using them for reducing any organ is an abuse and may cause dangerous side effects such as infection and oedema, he said.
The second category refers to substances used overseas but not yet endorsed in Thailand.
"Injections that are not clean may cause infections," Wanchai said.
He urged people to alert the FDA if they find any adverts for lipolysis injections.
Wanchai said instead of seeking such injections, people wishing to get slim should focus on food control and exercise.