"We would like to see more security personnel and more frequent patrols," said one of the leaders of the rally.

A wave of violence has hit the Muslim-dominated south in recent months, targeting police, teachers and monks.

In the latest incident, a teacher at a school in Pattani was shot dead in front of his students on Monday.

The rally took place in Pattani, one of four southern provinces affected by the violence, which has been blamed on Muslim militants.

The government has tried to step up security in southern schools in recent months, after a number of threats to teachers and students, as well as arson attacks on school buildings.

At least 1,000 soldiers and police have been deployed in schools since the academic year began in mid-May.

But this latest killing shows that teachers are still at risk.

Prime Minister Thaksin Shinawatra has assured teachers they will be protected.

Education Minister Adisai Bodharamik travelled to Pattani on Wednesday to meet local teaching representatives for further discussions.

More than 200 people have been killed in the violence in southern Thailand since January.

The unrest reached a peak on 28 April, when more than 100 suspected Islamic militants were killed when they launched raids on police posts and checkpoints.

Three Buddhist temples were bombed in mid-May, and an elderly Buddhist man was killed last month.