There are plenty of people that have come back and said "I talked to my airline and they said nothing is required." It's also well known that Thai Air doesn't require proof of onward travel.
You're right, it's not rocket science. You'll just be sent back home without being able to get on your flight since you didn't provide them with the REQUIRED proof of a ticket out of Thailand.
You need the 800,000 in your bank in order to apply for a non-O visa conversion in Thailand. Some offices require the money to be in your bank for 2 months already when you apply (mainly Jomtien/Pattaya).
If you are traveling as a tourist (tourist visa or visa exempt) then legally you are required to have proof of onward travel within the number of days you will receive upon arrival (60 days). Realistically, immigration only asks for this when they are looking for a reason to deny you entry, so it's very rare.
But it's very common for your airline to ask you for this, and if they ask you cannot provide it, they will not let you board your flight. You will need to contact your airline and ask them about their policy.
That doesn't make sense. The money is in the bank exactly for emergencies. They want to know you can support yourself in an emergency. If that money was already spent on an emergency, that means you will not have the money for the next emergency and may become Thailand's problem due to that fact.
Many years of very good reports. But within the last month or two, people have stated things have drastically changed. Transfers held up for weeks or months, and then at the end the transfer is cancelled and they have to file a claim with Deemoney to get the money transferred back into their accounts.
You need to ask your airline. If you're flying without a visa, they may require you to show proof that you are leaving Thailand within 60 days or they will not let you board your flight.