A second officer said police were not looking for a British man who had  travelled with Miller, contrary to UK media reports. “All of the British nationals are now on their way home,” provincial police chief Kiattipong Khawsamang said, adding they had been “cleared” as suspects.

The pair travelled to Koh Tao with friends and met each other on the island while staying in neighbouring rooms at Ocean View Bungalows, said police Major General Kiattipong Khawsamang.

“They went out to a bar and left together after 1am, according to closed circuit TV camera footage,” he said.

Police have released still images from surveillance cameras in the area. One showed what police said were the two victims walking together hand-in-hand. Another image from later in the morning showed a single man walking in the same direction.

Police said the man looked Asian and was considered a prime suspect, but investigators were pursuing several leads.

“We are focusing on migrant workers because of the surrounding witnesses and evidence, including the video footage,” Kiattipong said. “We are sweeping hotels, bars, businesses and residences of migrant workers on the beach to find the suspect.”

Another police official, Colonel Prachum Ruangthong, said investigators were also looking for a group of bar employees and had questioned a group of foreigners as well.

“This morning we surrounded three locations, including the residences of migrant workers, to search and collect DNA,” Prachum said on Tuesday.

On Monday night, about 100 local residents gathered on Sairee Beach for a candlelight vigil and said prayers for the young British couple close to the spot where their bodies were found.

The bodies of the victims, who arrived in Thailand on August 25, are being driven the 500km from southern Surat Thai province and are due in Bangkok later on Tuesday for forensic tests.

Southern regional police commander Panya could not confirm Thai television reports that police had seized an iPhone and blood-stained jeans after raiding rooms used by the Myanmese suspects.

Thai authorities frequently accuse migrants from Myanmar and Cambodia of committing crimes in the kingdom, where they make up a vast, poorly-paid and low-status workforce.

Koh Tao, home to stunning white sand beaches and azure waters, is popular with divers but is smaller and more laid-back than neighbouring Koh Phangan – which draws hordes of backpackers to its hedonistic full moon party.

On Tuesday Thai junta chief and prime minister Prayuth Chan-ocha appeared to call into question the victims’ conduct in addition to the perpetrators of the attack.

“We have to look into the behaviour of the other party too because this kind of incident should not happen to anybody and it has affected our image,” he said, referring to the two tourists.

Speaking a few hours later he said Thai authorities must tell “tourists when the safe times are to be outside, we have to help them understand.”

Defence Minister Prawit Wongsuwan said police were working “to make an arrest as soon as possible.”

The murders are likely to heap more misery on Thailand’s lucrative tourism industry, which has been battered in recent months after a prolonged political crisis ended in a coup.

The army swiftly blanketed the country with a curfew and strict martial law, frightening off visitors.

Although the curfew was soon lifted from key tourist hotspots, visitor numbers have yet to rebound and martial law remains in place.

Military leaders have vowed to restore the nation’s reputation as the “Land of Smiles” with a clean-up targeting tourist resorts after a series of complaints about scams, assaults and even police extortion.

Britain says Thailand is the country where its citizens are second most likely to require consular assistance if they visit, behind the Philippines.

There were 389 deaths of British nationals in Thailand in the year to March last year – about one for every 2,400 British visitors or residents – although that figure includes natural causes.

But it is rare for tourists to be murdered in Thailand, although it is not uncommon for visitors to die accidentally.

In July last year a 51-year-old American tourist was stabbed to death after an apparent row in a bar in Krabi, another popular tourist haven.

His death came just weeks after another American was slashed to death by a taxi driver in Bangkok after an apparent argument over the fare.

Additional reporting by Associated Press