A car bomb wounded seven people, including an Italian girl, when it exploded in the parking area of a shopping mall on the Thai tourist island of Samui, police said on Saturday.
The bomb was packed inside a Mazda pick-up truck and exploded late on Friday in the car park of the Central Festival mall on the island while late-night shoppers were inside the building.
Police said the car had been stolen from Yala, one of Thailand's three southernmost Muslim-majority provinces that have been scorched by a 10-year insurgency that has killed more than 6,300 people.
"It's a car bomb but we cannot confirm what type of explosive materials they used," lieutenant-general Prawut Thavornsiri, spokesman for Thai national police told AFP.
"The car used was Mazda pick-up truck stolen from Yala," he added, without specifying whether the blast was believed to be linked to the conflict hundreds of kilometres (miles) away.
Poonsak Sophonsasmorong of the island's disaster prevention office said "six Thais and a 12-year-old Italian girl were treated for minor injuries", adding that they had all been released from hospital.
Thai police are often accused of leaping to conclusions in the immediate aftermath of high-profile incidents.
The Thai force came under fire for bungling the initial investigation and leaking erroneous information to the media during the probe into the murder of two British backpackers on Koh Tao island last year.
A second policeman at the scene also said Friday's blast was caused by a car bomb.
Bomb squad experts scoured the debris early Saturday in the underground car park for clues about who might be behind the attack, which comes as Thailand's junta tries to reassure tourists about the kingdom's safety as a holiday destination following a coup last May.
Samui is a wildly popular tourist island in the Gulf of Thailand. Around 20 million visitors flock to Thailand each year and are a key part of the economy.
Although the military lifted martial law last week, it maintained sweeping security powers citing the threat of political unrest.
Hidden but deadly conflict
Thailand's southern provinces bordering Malaysia, some 400 kilometres (250 miles) south of Samui, is home to a festering insurgency pitting Muslim rebels against security forces.
The majority of the victims of the war, which is characterised by near-daily bombings, shootings and even beheadings, have been civilians, yet the highly localised conflict remains off the international radar.
Experts say that is in part because the insurgents, who are seeking greater autonomy, have not launched attacks in Thailand's better-known tourist areas outside of the South.
But deadly blasts have occasionally struck Hat Yai, the main commercial city in the south, which is popular with Malaysian tourists.
Thailand's junta says it is trying to reboot peace talks with a patchwork of Muslim militant groups from the culturally distinct south, which was annexed by Thailand a century ago.
But no date for the talks has been announced, while rights groups say killings of civilians and abuses by security forces are continuing.
Seven Thai security officials face murder charges after four unarmed Muslim men were gunned down in a botched raid on a remote farm in Pattani province in late March.
The case has revived the issue of extra-judicial killings in the south, which is cloaked by Thai security forces.
While the rebels eschew publicity, they have previously called for increased autonomy as well as an amnesty for their jailed fighters.