Four people are now known to have died in a series of bomb blasts in southern Thailand's commercial hub, Hat Yai.
A Canadian tourist was among those killed in Saturday evening's bombings, becoming the first Westerner to be killed by the separatist insurgency.
About 70 other people were injured in the blasts, several of them foreigners.
The blasts were the latest in a string of violent incidents in the restive south, where more than 1,500 people have been killed since January 2004.
Officials blame Muslim insurgents for much of the unrest, although criminal gangs are also thought to be behind some of the attacks.
'I feel lucky'
Thai media reported that the bombs were hidden in motorcycles and triggered by mobile phones.
There were six bombs in total - mostly placed near department stores and restaurants.
Television pictures showed the Odeon and Big C department stores on fire.
"I feel really lucky today," one Australian survivor told AFP news agency on Sunday, standing near the wreckage of the Brown Sugar Bar and Cafe, where he was drinking the night before.
The authorities had tightened security in the south over the weekend, fearing attacks to coincide with the anniversary of the foundation of one of the separatist groups there, the Gerakan Mujahideen Pattani (GMP).
A gathering to promote peace was also held on Saturday in Yala province, organised by the Thai army.
The bombs in Hat Yai, Songhkla province, were further north than the usual areas targeted by the insurgents - the provinces of Pattani, Yala and Narathiwat.
Hat Yai is anxious to promote itself as a tourist destination, but correspondents say it has struggled to attract visitors, as a result of a bomb attack on the city's airport in April last year.
"The numbers of tourists will decline," said Nimit Chaichirathikul, president of the Tourism Association in Songkhla.
"Every time a bomb goes off, it will certainly affect tourism. I already am hearing that hotels are getting cancellations since the bombings," he told the Associated Press.