And what makes you think that a passport control IO which is a special branch of immigration is trained to know the difference between a checking account or an investment account? They're going to see a whole bunch of money in an account and say okay
Honest to goodness people, either buy some adult diapers or put on your big boy pants and walk through immigration. Dial back the paranoia, smile, hand over your evisa and your passport
Chances are one in a thousand that you're going to be asked to show your bank account. Regardless even if you're unable to show it doesn't mean you'll be denied entry. But to be sure to have 20,000 baht cash or equivalent currency in your possession.
Possible but unlikely. You will definitely be asked for proof of location so make sure you're in the jurisdiction covered by the particular Embassy you're going to use.