Thai Prime Minister Thaksin Shinawatra has pledged an investigation to find out why early warnings were not issued ahead of Sunday's deadly tsunami.
Efforts are continuing to locate the missing and identify the dead
Thailand's death toll currently stands at 4,812, with just over half of the dead being foreign tourists, but Mr Thaksin warned it could reach 8,000.
Specialist DNA forensic teams from at least 12 states have now arrived in Thailand to help identify the dead.
But they are warning it could be a long and distressing process.
"There must be an investigation of the whole incident, how it happened, when it happened and why early warnings could not have been issued," Mr Thaksin said in his weekly radio address on Saturday.
Mr Thaksin's remarks follow allegations made by an unnamed member of the Thai meteorological department this week that a tsunami alert was not issued for fear of hurting the country's important tourism industry in case it turned out to be a false alarm.
None of the countries affected by the tsunami issued a warning.
Mr Thaksin said he had appointed a quake and tsunami expert, Samith Dhammasaroj, to establish an early warning system for all natural disasters.
"Some might say we are putting up fences after the cows have gone," he said. "But there are still some cows left and there will be more cows coming and we need to have a strong fence," he said.
The BBC's Dominic Hughes, on the Thai island of Phuket, says that in some places the devastation has been complete - remote coastal fishing villages have been entirely wiped out.
Meanwhile, the struggle to identify the dead continues. Our correspondent says so far the bodies of around 250 foreigners have been positively identified - just one in 10 of the total known to have died so far.
But it could be weeks if not months before all those killed in Thailand by last Sunday's tsunami are identified, rescue teams in the country have said.
The death toll is now more than 4,800, with another 6,000 missing.
It is now virtually impossible to identify the bodies by sight, so forensic experts are trying to use dental records, or match DNA samples provided by relatives of the missing.
But the bodies of the Thai victims - most of them Buddhists - have started to be cremated.
The traditional mourning rituals have been abandoned, with dozens of bodies being burnt together to reduce the risk of disease.
Across the country, New Year's celebrations were cancelled or toned down. In Phuket, hundreds of tourists left bars at midnight to join locals in spontaneous candle-lighting in the streets, the French news agency AFP reported.
At the same time, a huge clear-up operation is removing the rubble of collapsed buildings in Thailand's top tourism spots.
The country relies on tourism, and businesses are trying to revive the industry as soon as possible, our correspondent says.