The Great Expat Exodus

Thaiger link

Nothing yet from US embassy, but bets are on that it will happen soon.

Personally I'd always considered the letter a bit of a ripoff, when a bank book with a year's worth of deposits should suffice. 

The certified letter was a good cover for people who did not have the required money and lied under oath. 

Thai immigration will have to come up with alternate procedures to prove income.  Many expats, including myself, have the monthly income above the requirement, but are unable or unwilling to deposit yearly amounts into a Thai bank.

From my own experience of transferring yearly amounts, too many people want to borrow, not always return the loan.