I swear my driver did it in just under 90 minutes about a year ago. Granted, it was about midnight, and the roads were relatively empty. But I did fear for my life a few times. 🤣
If you only want to stay for 3 months, just come visa exempt, then either get an extension before your time is up (60 days), or go visit another country for a few days, then re enter Thailand for another 60 day exemption.
Probably a belated ?? "Customer background check" of some sort?
We in the banking world know the 3 letter acronym very well. KYC - Know Your Customer. Know where their main sources of income/deposits are coming from, and any large regular withdrawals, etc.
If you bring in over $20,000 USD cash (or equivalent), then you have to declare it, no matter how you are entering. Most countries have a similar requirement, although the amounts may differ.
The 10,000 to 20,000 BAHT is a different scenario, for tourists and visa exempt. They want to see that you can support yourself. They don't want to see credit cards or statements, they want to see cash. And there are no ATMs in BKK between the gate and Immigration. So you have to bring it with you. I once had to count out $500 USD in $50 notes right there on the immigration counter.
There IS however on the books 10,000 to 20,000 baht that they can request proof of on tourist or exempt entry. They want to see cash in pocket, not credit cards, etc.
Not asked nearly as often these days, but can still be asked for.