The heir to the Red Bull energy drink fortune flew to Singapore two days before he was due to face prosecutors over a fatal hit-and-run, according to Thai immigration authorities .
Airport authorities in Singapore have confirmed Vorayuth "Boss" Yoovidhya's private plane is still there.
When he left Bangkok, Vorayuth, 32, was not a fugitive, but on Friday authorities issued an arrest warrant and notified Interpol that he was wanted on charges of causing death by reckless driving and hit-and-run.
Thai police say they do not know if he has left Singapore, and Thailand's foreign minister said he has not revoked Vorayuth's passport, which means he still could travel internationally.
The arrest warrant came almost five years after Vorayuth allegedly left a motorcycle police officer dead after crashing into him with his Ferrari. His family, half-owners of the Red Bull empire, has an estimated wealth of more than 20 billion US dollars (£15 billion).
Lieutenant General Nathatorn Prousoontor, police commissioner at the Thai Immigration Bureau, said Vorayuth left Thailand at 3pm on April 25 on a private jet.
He left weeks after an investigation found he had been enjoying his family's jet-set life since the 2012 accident and days before he was due in court.
When he was approached a few weeks ago outside a family-owned home in London, Vorayuth refused to comment.
Earlier this year AP saw him and his family enjoying a 1,000 dollar (£775)-a-night holiday in Laos, and saw social media postings of him snowboarding in Japan, attending Grand Prix races with Red Bull and visiting beach resorts in south-east Asia.
All that time he was repeatedly telling prosecutors, through his lawyer, that he was sick or out of the country on business when called in to face charges.
Lt Gen Nathatorn said Vorayuth was allowed to fly out last week because the trip came before the arrest warrant was issued.
"The prosecutors are handling the case and there was no request to ban his travelling to us," he said. "We only have been informed that the arrest warrant was issued on Friday April 28, which is after he had left the country."
Although Singapore has no official extradition agreement with Thailand, Interpol officials said police can informally arrange through other means to apprehend him there.
Friends and family postings on social media show Vorayuth has been in Singapore every year since the accident, often at Formula 1 races, but also celebrating family birthdays and holidays.