Was the statement and closing certificate in a single .pdf file? You can only upload 1 file per section of the application form. Maybe resend the statement. I think the "other statement mentioned is for a sponsorship arrangement."
In the reset password dialog type your email address out, do not copy and paste. Ensure the entered captcha code is upper and lower case as seen. Search your emails for the registration confirmation email, use keyword "thaievisa"
If you have a history of back to back visa exempt entries and it looks like you're trying to live here on free stamps etc, then expect a grilling at immigration when you arrive. If you are an occasional visitor staying a month or two a couple times a year then you have nothing to be concerned about.