The latest blast ripped through a bustling market in the southern Yala province. A shopper was killed and five others were wounded.
"The bomb exploded about 7am and killed one Buddhist man and injured five others," a police official in the town of Tan Toh said.
He said the bomb was detonated by a mobile phone and the dead man was 63-years-old.
Police and witnesses said the first blast ripped through a crowded restaurant in the capital of Narthiwat province on Friday evening, injuring 16 people.
Some 40 minutes later a device went off in a general store at Tak Bai district while another exploded in the Bacho district of the province, but no one was hurt.
Thai security forces have been
accused of using excessive force
Coming hours after a Buddhist teacher was shot dead, the blasts further heightened fears of simmering violence since the deaths of 87 Muslim protesters on 25 October.
At least 27 people, almost all of them Buddhists, have been killed since 25 October.
And altogether, more than 540 people have died this year in a separatist-inspired rebellion in Thailand's southern provinces.
Media reports, meanwhile, said an independent commission investigating the deaths of the protesters last month had accused some security force members of firing directly into the crowd.
Commission member Isma-ae Ali said that gunshot wounds on seven of those killed suggested not all security members had fired in the air as the government had said.
The inquiry, however, is focusing primarily on 78 protesters who died of suffocation after being rounded up by the police.
Muslims make up 4% of the Thai population, but are in a majority in four southern provinces.
A separatist insurgency in the south has continued sporadically for decades and sparked into life again in January with a raid on an army depot by armed men who killed four soldiers and looted hundreds of weapons.