If the 500.000 Baht hasn’t been long enough in the account as that specific Embassy want, then you wait to apply until the money has been long enough in the account.
500.000 Baht is one of the most important requirements, no matter if workcation or soft power.
It says “INTENDED arrival date” and you can supply a flightnumber also, since it only tells the route of the flight, not the actual date or time ( just like busnumbers )