The attack came soon after the government in Bangkok said it would hire a public relations firm to improve Thailand's image abroad.
Surayud Chulanont, the Thai prime minister, said the government had hired a US public relations firm on a $600,000 three-month contract.
'Revenge' killing
Monday's night market bomb was hidden in the front basket of a motorcycle, which was parked in front of a Muslim food stall in the market in Muang district, police said.
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More than 2,000 people have been killed since
an uprising in the south flared in 2004 [EPA] |
Four of the 20 wounded had serious injuries.
The blast followed the bombing of a mosque on Saturday which killed a Muslim man and injured three others.
In a separate incident on Monday attackers killed two Buddhist villagers, beheading one of them, and left another note saying killing was in revenge for the mosque bombing.
On the same day one person was injured after a bomb exploded at a roadside restaurant in Narathiwat province.
Despite the recent spate of what appears to be tit-for-tat attacks in the south, Thai authorities have played down any suggestion that sectarian violence has broken out.
Instead, they have generally blamed Muslim fighters for attacks on both Buddhists and Muslims.
Thailand is overwhelmingly Buddhist, but Muslims are a majority in the south, where they have long complained of discrimination.
Since an uprising flared in the country's Muslim-majority southernmost provinces in early 2004, near-daily bombings, drive-by shootings and other attacks have killed more than 2,000 people.
Lobbyists
The government's decision to fund an international public relations drive follows a move three months ago by Thaksin Shinawatra, the former prime minister ousted in a coup last September.
He has hired two Washington lobbyists, purportedly to study the international legal and political issues surrounding his overthrow.
Thaksin has denied having any further political ambitions, but has travelled to many capitals across Europe and Asia since he was deposed, meeting government and business leaders.
Surayud, Thaksin's military-appointed successor, indicated one reason for the public relations move was to counter any lobbying on Thaksin's behalf.
It may also be to counter moves by US pharmaceutical companies to shame Thailand for breaking Aids drugs patents.
A lobby supporting the US pharmaceutical industry placed an advertisement in the Wall Street Journal last week criticising the Thai government's breaking of patents.