More than 1,000 schools in southern Thailand have closed as tensions continue to rise in the area following a string of attacks.
Schools were targeted in attacks earlier this month
Teachers said they were terrified by recent death threats against them, and the government said it was considering imposing a curfew in the south.
The most recent violence has been directed at Buddhist monks.
The attacks, which began on 4 January, have been blamed by ministers on both Muslim separatists and bandits.
A teacher at one school in Pattani province told The Nation newspaper that she had received leaflets threatening attacks on teachers and students in the province.
"This is the worst time I have had in my entire career for 22 years," the teacher said.
Home to most of Thailand's 4% Muslim minority
Muslim rebels fought the government up to the mid-80s
Area beset by poverty and poor relations between local communities and officials
"I am afraid of leaving my home or my workplace," said the woman, who is Buddhist.
Last week, three Buddhist monks, including a 13-year-old novice, were hacked to death.
Media reports said on Wednesday as many as 20 youths had been detained for questioning about the recent killings, but none had been charged.
"The deadlock comes because local people don't want to give us information or tips," Thai Prime Minister Thaksin Shinawatra told reporters.
He added that local Muslim leaders had told him some of the groups behind the violence had received funding from abroad.
But Surin Pitsuwan, a former Thai foreign minister who has just visited the troubled south and a Muslim, said the prime minister did not have the right to accuse local people of not cooperating with police.
"They cannot trust the government. They have not benefited from the process of law, " he told the BBC World Service's East Asia Today programme.
Dr Surin said that problems in the south had become more serious because of what he called "heavy-handed tactics" by the central government.
Asked if the international war on terrorism lay behind the recent Muslim unrest in the south, Dr Surin said there was an "element of that." But he felt the real source of the problem was poverty, unemployment, and local feelings of "being ignored and living in despair".
Pattani, Yala and Narathiwat provinces were put under martial law earlier this month, but Thai Defence Minister Thammarak Isarangkura na Ayudhaya said a curfew was being considered as well to assist police operations.