22/09/2014 06:26 BST | Updated 22/09/2014 06:59 BST

Murdered Brit David Miller 'Was Trying To Help Fellow Victim' Hannah Witheridge When Both Were Killed In Thailand, Father Believes

The father of a British man murdered in Thailand believes his son had stepped in to help his fellow victim when they were both brutally killed on an island.

Ian Miller said it was in his 24-year-old son David's character to help, and claimed that was probably the circumstance when he and Hannah Witheridge were murdered in Koh Tao a week ago.

He told the Daily Mail: "It has become clearer and clearer that it is quite likely David was stepping in to help a girl who was in trouble. That would be absolutely in his character."

David Miller

A Thai forensic investigator examines a bottle of beer as he inspects a hotel room where one of two British backpackers stayed

The body of Witheridge, 23, has been brought back to the UK, her family said, as they released a statement saying they were "broken" by the tragedy.

While Thai media reports suggest there are now two main suspects in the investigation Police Colonel Kissana Phathanacharoen said: "There are more than two suspects. It is too early to say how many suspects we are looking at."

Yesterday the force said they are investigating new evidence suggesting that the murders may have been due to "sexual jealousy".

A spokesman for the Royal Thai Police said that the force was also looking into claims that the pair had a row with a Thai man in a bar before they were killed.

Phathanacharoen said: "We have discovered fresh evidence which could lead to a new suspect who may have had a relationship or one night stand with Hannah or one of her friends or David the night before they were killed. We have asked the Metropolitan Police to go back and make enquiries of Hannah's friends on this matter.

"The liaison officer here in Bangkok is working on getting that statement. The faster we get it, the faster we may be able to get the bad guy. No lines of inquiry can be ruled out and we believe these crimes could have been motivated by sexual jealousy.

Hannah Witheridge

"Police have been made aware of reports that Hannah and David had a fight in a bar with a Thai man before they were killed, but cannot confirm if they are true."

Miller said his family had not been given much information from Thai police on the progress of the investigation. Phathanacharoen said he would be happy to speak to Miller and pass on any information about the investigation.

Post-mortem examinations revealed that Witheridge, from Great Yarmouth, Norfolk, died from head wounds while Miller, from Jersey, was killed by severe blows to the head and drowning. A bloodstained garden hoe, believed to be the murder weapon, was found nearby.

Thai police are offering a cash reward worth about £4,000 for information that leads to the arrest of the suspects. Around 150 officers have been deployed on the island and senior police officials have met Witheridge's family.

Police said on Saturday they were looking for more than one suspect following unconfirmed reports that the DNA of two Asian men had been found on Witheridge's body.

A group of Burmese migrants who were interviewed by police after bloodstains were found on their clothes have also been eliminated from inquiries. No matches were found between them and DNA found on Witheridge and a cigarette butt at the scene.

Police had previously said they were looking for three Westerners who were seen playing a guitar near the scene on Koh Tao's main Sairee beach.

Last week Thailand's military ruler was forced to apologise for suggesting that foreign visitors to his country's world-famous beaches might be unsafe wearing bikinis.

In the face of mounting criticism, General Prayuth Chan-ocha said: ''I apologise that I have spoken too harshly ... I didn't mean to criticise or look down on anyone. Today I can guarantee that Thailand is still safe ... I wanted to warn (the tourists) to be careful.''