Ex-NBA exec's son was vacationing in Thailand with TikTok star Daniel Mac when ... trends now

Two American boys killed in a horror head-on motorbike crash in Thailand were on a three-week adventure with their TikTok star friend.

Elias Giangrande, 28, and Jack Niehaus, 25, died instantly when they collided with a minivan taxi after leaving the famous Full Moon Party on Wednesday.

Jack ran out of petrol on the way to their hotel on Koh Pha Ngan and Elias came back to give him a lift along the narrow, dimly lit road about 4.30am.

Local police alleged they were 'drunk and speeding' without wearing helmets, but are yet to receive the results of blood alcohol tests.

Elias, son of former NBA executive Gregory Giangrande, and Jack were holidaying with TikTok star Daniel Macdonald, known as Daniel Mac online, and a fourth friend.

Daniel posts skits and luxury car reviews for his 14 million TikTok fans and 2.6 million Instagram followers. He flew home to Los Angeles soon after the crash.

Jack's sister Priya Niehaus said her family last saw him alive in an Instagram story Daniel posted about two hours before the crash.

'He was at the party and there was a jump rope with fire on it and he was jumping over it, smiling and laughing, really happy,' she told DailyMail.com.

Priya said the four close friends often traveled together and left on April 17, starting in Taiwan and planning to go to the Philippines and Japan after Thailand.

'He used all his vacation days and they were going on a three-week adventure through Asia,' she said.

'They love traveling together, they tried to go to Burning Man but couldn't get tickets.'

Gregory Giangrande, former vice president of HarperCollins and a New York Post columnist, flew to Thailand as soon as he heard about the crash, and is overseeing the repatriation.

'He's getting our boys home safe,' Priya said. 'He's unable to speak very much, he's in tears, like us he's not doing well. His wife didn't come, she just can't.'

The bodies spent days sitting in 'horrible, awful conditions' at a rescue center, and the small remote island doesn't even have a proper police station.

Priya questioned whether the pair were really drunk driving, as the police alleged, as the toxicology report was not yet completed.

'They're both very smart boys, they don't usually do anything dangerous,' she said.

'Elias was always the first to come help people and that's why he came to help my brother.'

The pair met through Daniel, who studied abroad with Jack and later introduced them about three years ago. 

The last time Jack's family saw him together alive was his 25th birthday on March 21, just a few weeks before his death.

He visited the family home on Bainbridge Island, Washington, from his home in Seattle and had dinner with Priya, his parents Troy and Nicole, and his grandmother.

Troy saw him the day he left, when he talked about how excited he was for the trip as he had never been to Asia, and was particularly keen to see Japan.

The bodies were moved from the small island to the Thai capital Bangkok on Friday, from where they will be repatriated to the US.

Jack's remains will be cremated at a Buddhist ceremony, but Elias' family was yet to decide what to do with his body.

Jack's family described him as 'a son, a brother, and most of all everyone's best friend'.

'Think of all the best qualities of a human being, then add a cheeky joke, and a never ending smile,' they said.

'He had an aspiring career in private wealth at UBS, but his passions were travel, racing, and he dreamt of having a family of his own.

'Jack had a positive impact on everyone he encountered, and we will miss that, along with his selflessness.

'He was a ray of sunshine no matter the circumstances and most of all he was inclusive, loving, and kind to all. He may have only had 25 years, but man were those years a true gift.'

Jack Niehaus is a wealth management associate at UBS bank who previously worked as a client service associate for investment company Morgan Stanley.