Answer: Maybe. There's no such thing as an "es" chord in English, but there are programs that use "es" or "s" to indicate a flat when using typewritten characters. Probably they do that to avoid confusion between the note "b" and the use of the letter "b" as a flat symbol; "es" or "s" is the German abbreviation for "flat." So that is intended to be a Bb chord. I think it would be safer to write it as Bb. As you see, not every musician is going to know right off what "Bes" means.