Bomb blasts were among 23 coordinated attacks that rocked Muslim-majority southern Thailand early on Friday, a security officer said, just hours after King Maha Vajiralongkorn signed a new constitution as a step towards ending military rule.

Police reported no casualties in the region, site of a recent upsurge in a decades-old Muslim separatist insurgency that had voted the most strongly against the new constitution at a referendum last year.

"The incidents are aimed to create disturbances," Pramote Prom-in, a spokesman for regional security forces, told Reuters. "They want to destroy the government's credibility and create fear among people."

There was no immediate claim of responsibility and security forces said they could not yet identify which insurgent group was to blame.

The attacks were scattered across 19 districts in the southern region, grouping the provinces of Yala, Pattani and Narathiwat, and the nearby province of Songkhla, he said.

A large number of co-ordinated attacks in the region is unusual. Complete details were not immediately available, but they ranged from bomb explosions at 52 electricity poles, triggering widespread regional power cuts, to several tyre-burning incidents, Pramote added.

On Thursday, Thailand's king signed into law a military-backed constitution, an essential step towards an election the ruling junta has promised will restore democracy after the 12th successful coup in little over 80 years.

The new constitution is the Southeast Asian country's 20th since the end of absolute monarchy in 1932, and critics say it will still give the generals a powerful say over Thai politics for years, if not decades.

Voters in the most heavily Muslim parts of Thailand were among the few to reject the draft constitution in last year's referendum.

The timing of the attacks just hours after the constitution was proclaimed was curious, said Defence Minister Prawit Wongsuwan, but there was no conclusive evidence it was a motive.

A Malay Muslim separatist insurgency in the three southern provinces has killed more than 6,500 since it escalated in 2004, independent monitoring group Deep South Watch says.

On Monday, police reported what they called the biggest insurgent attack in the south in years, when about 30 people fired more than 500 shots into a police booth.

In February, the government of the Buddhist-majority country struck a deal with MARA Patani, an umbrella group that says it speaks for the insurgents, but other separatists rejected it.