The man, who was off duty at the time, is the second canvasser to be killed this month, although the authorities said it was unclear whether the latest attack was linked to Thailand’s July 3 vote.
The 55-year-old Buddhist, who was a local sub-district leader, was killed by unknown assailants in a pick-up truck while riding his motorbike home with his wife from a wedding in Muang District in Yala Province, police said.
Militants in the area often target people on motorbikes.
The victim was a canvasser for the ruling Democrat Party led by Prime Minister Abhisit Vejjajiva, who was scheduled to arrive in the area late Monday for a tour of three southernmost provinces that have been under a state of emergency since 2005.
More than 4,500 people, both Muslims and Buddhists, have died in almost daily attacks since insurgents launched an uprising in Thailand’s deep south near the Malaysian border in early 2004.
Critics accuse the government of failing to address the grievances of Thailand’s Malay Muslim minority, including alleged abuses by the military and a perceived lack of respect for their ethnic identity, language and religion.
Police have said they will deploy 100,000 officers across the country to guard polling stations for the election. Many candidates have requested protection.
An opposition politician was shot and wounded in May in what the authorities said appeared to be a politically motivated attack.
Last week a canvasser for the Bhumjaithai Party, a key coalition partner of Abhisit’s Democrats, was shot dead on Bangkok’s Khao San Road, an area popular with foreign backpackers.
The election will be the first since Thailand was rocked by its deadliest political unrest in decades last year, when more than 90 people died in street clashes between armed police and opposition protesters.