His main rival, opposition leader Kem Sokha (pictured), held a rally in Phnom Penh, promising to fight corruption.
The election will give an indication of Hun Sen’s support ahead of next year’s national vote.
More than 1,600 communes, clusters of villages, will vote next month with the opposition Cambodia National Rescue Party (CNRP) hoping to weaken Hun Sen’s grip on power, describing it as corrupt and repressive.
Hun Sen’s Cambodian People’s Party (CPP) is still supported by many older Cambodians who fear change could reopen historic wounds from the Khmer Rouge era and derail economic growth.
Kem Sokha’s CNRP has faced numerous legal cases since narrowly losing the disputed 2013 general election.
Speaking to thousands of supporters in Phnom Penh, Kem Sokha said political change was achievable.
“We have travelled through obstacles, rainstorms and lightning … but the CNRP has managed to survive and is stepping forward,” Kem Sokha said.
Kem Sokha took over the party leadership in March after his successor, Sam Rainsy, stepped down and fled into exile to avoid a string of legal cases that could have led to the CNRP being outlawed.
The CPP itself held a rally in Phnom Penh, attracting thousands.
Hun Sen has overseen as Cambodia became one of Asean’s fastest growing economies with a young population while many complain about corruption and rights abuses as Hun Sen’s family and friends have grown hugely wealthy over the years.
A former Khmer Rouge cadre, Hun Sen fled Cambodia in 1977 and returned with the Vietnamese military during that country’s war against the savage regime in 1979. He was first appointed foreign minister and was named prime minister in the Vietnamese-supported government in 1985.
US State Department spokeswoman for East Asia, Alicia Edwards, urged Phnom Penh to “guarantee a political space free from threats or intimidation” and respect freedom of expression for all citizens.
Cambodia’s defence minister has reportedly warned that the military will “smash the teeth” of anyone protesting against a CPP win.
Sam Rainsy, former president of the CNRP, and Kem Sokha, then vice president. Picture credit: Wikimedia