Random thoughts as someone who worked for a number of years in Thailand assisting foreigners in crisis.
- There are so so so many foreigners living and travelling in Bangkok. He wouldn't stand out unless he was exhibiting some extreme kind of behaviour.
- We saw a LOT of young men and a few young women with sudden onset mental health episodes usually linked to lifestyle factors like trying some new drug. I cannot count the number of young men who have had a complete breakdown in their mental health in Thailand and they had no hint before they travelled there. I've seen so much extreme behaviours - including booking and then missing flights - and it is so common - I would not rule it out.
- Also very common: men drawn in by an attractive 'date' then assaulted, robbed, sometimes drugged by them or their accomplices. Rarely someone might be killed. The Thai sex industry is everywhere and many, many tourists participate during their holidays. They do not tell their families or partners back home until forced to, when something goes wrong.
- Self harm - I have seen a lot of very sad outcomes.
- Gambling gangs/extortion - make friends with some friendly young foreigners who are on holidays, invite them somewhere, start with a friendly card game that gets progressively more threatening. March them to ATMs and demand money and maintain control of them until they pay.
- Drug deals gone wrong and drug intake gone wrong (overdoses).
- Taxi driver incidents: If he was enroute to the airport when his phone pinged, I hope Simon didn't get in an argument with a taxi driver. There are some pretty vicious taxi gangs out there and it's known that it's one of the few jobs that ex-prison inmates can easily get. Usually it's Thai people affected, but this was a historical, quite well known instance involving a foreigner
www.bangkokpost.com/thailand/politics/359730/aftermath-of-expat-killing
- He could be in hospital as an identified person; probably unlikely if he was enroute to the airport as he would have had ID in the car. Hospitals in Thailand will only provide limited treatment to foreigners without a guarantee of payment. I feel like this is less likely as social media is very widely used in Thailand and the case would have popped up in local media.
- Maybe he's arrested and the Thai government are just taking time to notify the British Embassy. IMHO that would be highly unusual, Bangkok police are usually pretty good at letting foreigners notify their embassies if they are detained, particularly in Bangkok.
Honestly based on the numbers I dealt with over a 4 year period, statistically I'd guess mental health issue, though it's obviously impossible to say given the limited information we have here.