Wahama Ratoo, 44, the religious teacher turned farmer, was shot by a sniper around 4.15 pm (local time) on Thursday while tending to his herd in a jungle near his house in Sakhon district of Narathiwat province, police said.
Police said they were investigating suspects and a motive for the attack, but believed Wahama died instantly after being shot several times.
Teacher Salaema Dauwa, 61, from Narathiwat province was shot dead in his car on Wednesday evening along with his driver, 24-year-old Adisorn Dala, police said.
Two armed men on a motorcycle followed the men from Salaema's house before shooting them in Rue Sao district as they headed to a mosque where Salaema taught a course on Islam.
More than 860 people have been killed in nearly 20 months of fighting in the southernmost provinces of Thailand.
Meanwhile, after more than 10 hours of debate early on Thursday, Thai parliamentarians passed a controversial emergency decree aimed at stemming the violence in the southern areas.
The decree was controversially enacted in July while parliament was on recess, replacing martial law in the provinces.
"We cannot agree with the decree as it is not the way to bring back peace to the community - the way is by creating trust"
The opposition criticised the emergency measures during the debate, saying they would never resolve the problems in the south and that the only solution was to rebuild trust with the community.
"We cannot agree with the decree as it is not the way to bring back peace to the community - the way is by creating trust," opposition leader Abhisit Vejjajiva told parliament.
A leading UN human rights panel in July sharply criticised the decree, which allows authorities to detain suspects for up to 30 days without charge, search and arrest without warrants, and tap phones.