The National Anti-Corruption Commission has launched an inquiry into the actions of an NACC assistant secretary-general seen in an internet video clip aiming a pistol at another driver in the grounds of the government complex in Laksi district, Bangkok, last week.
The video was recorded by the dashboard camera of a following taxi, driven by the man being threatened, on the afternoon of Oct 10.
The man with the pistol, the driver of a black Honda Accord, has been identified as Piset Nakapan, a 52-year-old assistant to NACC secretary-general Worawit Sukbun.
Mr Worawit said on Wednesday the incident was a "personal action, nothing to do with exercising authority while on duty".
A fact-finding panel had been set up to look into the matter. It was led by NACC deputy secretary-general Natcha Koetsi and had 15 days to present its findings.
Mr Worawit said he believed Mr Piset was licensed to own a firearm because he had worked as an inquiry officer.
However, Thung Song Hong deputy police chief Suban Athiset said Mr Piset had been charged with carrying a weapon in public without good reason, and intimidating another person.
The suspect was questioned by Pol Lt Col Suban on Tuesday afternoon and admitted he and his wife were both in the Honda sedan involved in the incident, but said he had no intention of "pulling the trigger".
According to Pol Lt Col Suban, Mr Piset said he got out of his car and pointed his pistol at the taxi driver to stop him from following him.
According to Mr Piset's account, the taxi overtook and cut in front of his car before turning into the government complex grounds. The taxi then stopped suddenly, causing Mr Piset to toot his horn to warn the driver before overtaking him, because he was "hastening" to some work in Building B.
He resorted to showing his pistol after the taxi continued following him and the driver flashed his lights in a sign of dissatisfaction.
In the video clip, the Honda car is seen rapidly overtaking the taxi in the left lane before the incident.
Pol Lt Col Suban said the taxi driver will be called in for questioning.