THE six junior traffic policemen who walked into the newsroom of ITV last Thursday did not look as if they were radical activists bent on exposing the corrupt practices of the country's 200,000-strong police force. In fact they were polite, even slightly shy, and had a very simple message: ''We can't stand being forced into a daily corruption scandal any more.''

As it turned out, their desperate plea for public understanding and protection from unscrupulous orders from their superiors could turn out to be the onset of a long overdue major overhaul of the police department, if the interior minister and the national police chief mean what they said in the aftermath of the ''corruption scandals on the expressway''.

Nobody will be spared. Heads will roll. This time around it will not be just cosmetic changes, they promised.

Will they live up to their pledge? History would suggest otherwise, but this was the first time in recent history that a television camera actually caught the scam in action when ITV showed four officers stationed at Sathupradit expressway entrance receiving cash bribes dropped on the road by passing motorists.

This was also the first time that a sizeable number of dissidents in a police unit -- 50 out of 150 -- at the grass-roots level had mustered enough courage to put their names on a petition to point an accusing finger at their superiors who had, they claimed, forced them into a daily corrupt routine.

Under normal circumstances, these cops might have been able to issue about 20 tickets to motorists for having excessive exhaust levels a day. Then, one day last October, one of their bosses issued a new order, setting a ''daily target'' of 50 to 70 tickets a day. It was not in the order, but the implication was that any underperformer would be punished with a transfer to a less ''lucrative'' post.

To achieve that daily goal, the policemen on the beat had no choice but to make culprits of innocent motorists. One of them told me: ''Only about five out of every 20 motorists we stopped might actually have excessive exhaust levels. With the other 15, we had to make things up. They were our scapegoats, our victims. Some of them cried and plead for sympathy because they said they had just installed their exhaust pipes, but there was nothing we could do. We had a target to meet every day.''

Innocent citizens, in other words, were being framed. The public was being robbed in broad daylight on the expressway. Of course the decision to force all this out into the open had not been driven by pure altruism.

''We have also been cheated of our reward money. For each fine, we should get a 20-per-cent share, Bt200 from the Bt1,000 fine or around Bt4,000 every 15 days, but all we have been getting is Bt500 to Bt700 for each period,'' one of them claimed.

There is also the mysterious disappearance of 50 per cent of the fine which is by law paid to ''informants'' leading to an arrest.

Who are the informants on the expressway? I asked. One of them responded: ''We don't know. There usually aren't any informants on public thoroughfares anyway, so we guess somebody just made up names and pocketed the 50 per cent of the reward money.''

If they knew it was the wrong thing to do, why did they not talk to their boss directly about it?

''If we'd raised the issue with him, he would have had us transferred. There was no way we could have confronted him with the problem. He knew and we knew that it was physically impossible to stop 70 cars on the expressway every day, check them for their exhaust levels, find them guilty and issue tickets to them,'' another member of the group said, adding ominously: ''There was this friend of ours who tried to speak to the boss, and he was asked whether he wanted to be reassigned to the border. Another guy was simply asked whether he knew what premature death was ... and the death threat could not be taken lightly.''

Perhaps it was unfair to blame everything on the boss. Perhaps there was something wrong with the exhaust-detectors. Perhaps the equipment was old, rusty and broken down.

''No,'' said the youngest policeman in the group, speaking for the first time, ''no, there was nothing wrong with the equipment. There was something wrong with us as human beings.''

BY SUTHICHAI YOON

The Nation