Gunman burst into a house in Yala province, and killed four people
Nine people have died in the past 24 hours in a wave of attacks by suspected Islamic militants in southern Thailand.
The latest violence coincides with the fifth anniversary of an attack on the Krue Se mosque, which marked a sharp escalation in the separatist conflict.
It was the first big clash between the security forces and militants, and more than 100 people died in just one day.
About 3,500 people have died since then and successive governments have made little progress in stemming the unrest.
Thailand annexed the three southern provinces - Narathiwat, Yala and Pattani - in 1902, but the vast majority of people there are Muslim and speak a Malay dialect, in contrast to the Buddhist Thai speakers in the rest of the country.
Insurgents target people they perceive to be collaborating with the Bangkok government - using bomb blasts, beheadings and shootings.
They also try to force Buddhist residents from the area, with the aim of ultimately establishing a separate Islamic state.
Gunmen stormed into a house in Yala province late on Monday, opening fire on a Muslim family and killing four people.
Two men were later found dead outside a nearby mosque.
In other incidents, a Buddhist government official was shot dead in Pattani province, a Muslim man was fatally shot while watching a football match in Yala and another man was killed nearby in a drive-by shooting.
According to the BBC correspondent in Bangkok, Jonathan Head, there is nothing remarkable about the attacks of the past 24 hours.
Now in its sixth year, the renewed war in Thailand's south continues to exact a heavy toll on the local inhabitants with relentless regularity, our correspondent says.
Early on Monday there were 11 co-ordinated attacks on schools and electricity substations. On Saturday a bomb blast injured 15 people.
The bloody assault on the Krue Se mosque by Thai security forces on 28 April 2004 is seen as an important point in the long-running conflict, leading to a marked escalation in the violence.
Security forces stormed the mosque and killed 32 Muslims who had barricaded themselves inside. More than 70 others died in separate incidents on the same day.
"Security forces are taking special precautions and are on high alert on the [Krue Se] anniversary," army spokesman Parinya told the Associated Press on Tuesday.
Human rights groups argue that the government's failure to punish any members of the security forces for abuses against civilians has alienated the population in Thailand's deep south.
But other analysts believe the militants, who operate in small cells affiliated with Islamic schools, are not interested in negotiating with the government, whatever concessions it makes.