Image copyright EPA Image caption Mr Vorayuth has repeatedly failed to turn up to face charges

Singapore authorities say the Thai heir to the Red Bull empire Vorayuth Yoovidhaya, who is wanted in Thailand, is not in the city-state.

Thai police said he had travelled to Singapore from Bangkok last week, days before they issued an arrest warrant.

His private plane was reportedly still in Singapore as of Tuesday.

Mr Vorayuth is at the centre of a criminal case closely watched by many Thais. He is accused of knocking down and killing a police officer in 2012.

A spokeswoman for the Singapore police told the BBC on Thursday that Mr Vorayuth "is not in Singapore".

She added that they would "provide the necessary assistance and support to the Thai authorities in accordance with our laws".

Thai police have summoned Mr Vorayuth multiple times to face charges, but he has repeatedly failed to attend these meetings.

Mr Vorayuth's representatives have said each time that he was either away for business or too ill to meet police.

Thai investigators are now seeking to cancel his passport.

The case has attracted criticism that the Thai elite enjoy special treatment from authorities.

Analysis: Jonathan Head, BBC News, Bangkok

Image copyright EPA Image caption Mr Vorayuth's badly-dented grey Ferrari was found in his family's compound in Bangkok in 2012 shortly after the accident

Even if the Thai authorities try to bring Vorayuth Yoovidhaya back to face charges related to the hit-and-run killing of a policeman in 2012, the chances of him being sentenced, let alone imprisoned, are not high. Wealthy defendants in Thailand have shown time and again that they can evade justice.

Ask Vatana Asavahame, a veteran politician who was given a 10-year sentence in 2008 for a notorious corruption case. He simply moved overseas, and has never served a day in prison.

Or ask Somchai Khunpleum, better known as Kamnan Poh, the godfather who once controlled much of the business around Pattaya. He was convicted of ordering the murder of a political rival in 2004. But it was only in 2013 that the police caught him, at an expressway toll-booth, driving to Bangkok for routine medical treatment. He has since been allowed to serve his 30-year sentence in a hospital close to his home.

Then there are the other cases of rich kids involved in road accidents.

In July 2007 Kanpitak "Moo Ham" Patchimsawas, then 22, drove his Mercedes car into a crowd of passengers after an argument with the bus driver, killing one woman. He went to prison to serve a two-year sentence in only 2015.

In December 2010 Orachorn Devahastin Na Ayudhya, then 16, collided with a minivan while driving without a licence. Nine passengers in the van died. She was given a suspended jail sentence and less than 200 hours of community service.

Last year, a car driven by Janepob Veraporn was caught on a dashcam slamming at very high speed into the rear of another car in the slow lane of an expressway north of Bangkok. The other car burst into flames, killing the two postgraduate students inside. At the scene, Janepob was allowed by the police to refuse both a drug and alcohol test. After a massive public outcry, he was charged, and is currently on trial.

By contrast, a middle-aged couple from Thailand's north-east caught after picking mushrooms in a national park in 2010 were each given a 15-year prison sentence. They confessed to illegal logging on the advice of their lawyer, who said it would reduce their sentence, but they say they took only the mushrooms. This week, their sentence was reduced to five years.