The under-reported rebellion waged by Malay Muslim insurgents against the Buddhist-majority Thai state has killed more than 6,800 people, mostly civilians, since it erupted 13 years ago.
That toll rose Thursday after suspected militants ambushed the car of a deputy village headman, shooting him dead along with his eight-year-old son, wife and sister-in-law.
The family were driving to school on a remote road in the Ruso district of Narathiwat province when the gunmen attacked.
The ambush provoked outrage from religious leaders and civil society groups from both the Muslim and Buddhist communities, who came together for Friday's march through Ruso.
Dozens of local school children also joined the demonstration, carrying a banner that said "stop the shooting, stop the killing".
"The aim of the rally is to denounce the killing of innocent people," Colonel Ruangsak Buadaeng, a local police commander, told AFP.
Thursday also saw a 44-year-old Muslim leader killed in a drive-by shooting and three plainclothes soldiers gunned down in front of stunned shoppers at a night market in Pattani province.
The insurgents, who operate in tight and secretive cells, rarely claim their attacks.
Shootings are frequent but it is often hard to work out whether they are related to the rebellion, criminal activity or personal disputes in the region.
But Thursday's wave of violence appeared timed to undermine recent gains made in peace talks between the army and the Mara Patani -- an umbrella group claiming to represent the insurgents.
The Thai army and the Mara Patani this week agreed to create a limited "safety zone" in the region, as a trust building measure.
The deal, tantamount to a highly localised ceasefire, was a small but rare step forward in years of stuttering talks.
But analysts say the Mara do not represent the most active armed militant faction and have played down the significance of the "safety zone" announcement.
The Malay Muslim majority deep south was colonised by Thailand over a century ago.
Locals accuse Thailand of steam rolling their unique identity and culture as well as rights abuses.
Insurgents mostly aim their attacks at security forces, local officials and public school teachers, who are viewed as collaborators with the state.
Last September a bomb planted outside a school in Narathiwat province left three dead, including a four-year-old girl, triggering widespread condemnation.
