You could apply for the DTV using one of the soft power options. Other than that the Thai Privilege visa is probably your best bet but monthly income won't help. You need to show money in the bank
Get a letter from the company stating your last day of work then go and cancel your work permit, take the documentation from the Labour Department along with the letter and go and cancel your Non-B extension of stay. You can do this in advance, otherwise just leave on the day you cancel everything
you have to be careful printing out from the app as it only gives the current month to date and the previous 11 months (at least from Bangkok Bank) so might not cover everything you need. Immigration may also want to see it stamped by the bank anyway. Plus you need a letter from the bank highlighting your monthly transfers