Thirty minutes after the first bomb was detonated in a parking lot near a hotel in the coastal town of Pattani, a second bomb exploded in a truck parked at the hotel entrance, killing one Thai and injuring 30 others.

The attack late on Tuesday night came less than two weeks after a series of co-ordinated bombings and fires in tourist areas in seven Thai provinces, including the resort of Phuket, the most popular destination in Thailand for Australian tourists.

Thai police say most of the suspects in the August 11 and 12 attacks that killed four people and injured 30 are Muslims from the southernmost Malay-majority provinces of Yala, Narathiwat and Pattani, where almost 7000 people have been killed as Malay insurgents have waged a separatist war since 2004.

But Thailand's military government has played down evidence pointing to young militants linked to the Patani-Malay National Revolutionary Front (BRN), whose leaders have rejected a faltering peace process.

"We have to investigate further to determine whether this group is involved in not," said Prime Minister Prayuth Chan-ocha, a former general who led a 2014 coup to topple the democratically-elected government of Yingluck Shinawatra.

The government is worried that publicity about the militants possibility widening the conflict to target tourist areas will hit the tourism industry, which accounts for well over 10 per cent of the country's economy.

The government characterises the insurgency as "disturbances" carried out by criminals so as to minimise its political implications.

Bombings and targeted assassinations are a way of life in the southernmost provinces but Tuesday night's bombs were unusually lethal by comparison, analysts said.

Matt Wheeler, a South-east Asia security analysts for the International Crisis Group, said that if, as the available information indicates, militants perpetrated the recent attacks, then the conflict has entered a disturbing new phase.

"For 13 years the insurgency has had little effect on the lives of most Thais outside the deep south," Mr Wheeler said.

"Now a wider insurgency risks stoking militant Buddhism and sectarian conflict."

Police say that at least 20 southern militants carried out the co-ordinated attacks but have only issued a warrant for the arrest of one suspect, Ahama Lenga, from Narathiwat, who is accused of planting bombs in the Patong tourist area on Phuket.

In the latest bombings in Pattani, 1050 kilometres south of Bangkok, the militants appear to be signalling to the government that there will be no let-up in the attacks until Bangkok agrees to engage them.

The BRN's ageing leaders, who see the current peace process as a sham, never claim responsibility for their attacks.

In 2013 they demanded in a YouTube video the establishment of a new independent state encompassing the former Sultanate of Patani​, which was formally recognised as part of the kingdom of Siam in the early 20th century.

Mr Wheeler said it would be short-sighted and self-defeating of the generals running Thailand to insist on dismissing the August 11 and 12 attacks as a partisan vendetta unconnected to the conflict in the south.

"They should recognise the insurgency as a political problem requiring a political solution," he said.

"That means restoring the rights of freedom of expression and assembly to Thai citizens, engaging in genuine dialogue with militants and finding ways to devolve power to the region."

Australia's smartraveller.gov.au is warning Australians not to travel to Yala, Pattani, Narathiwat and Songkhla provinces and to exercise a high degree of caution in other regions in Thailand, including avoiding crowded places.