Hi Hiep,
Thanks for writing in, happy to help.
First, most schools traditionally only consider your highest GMAT performance, so you should feel that you can retake without consequences should you not raise your score.
While your theory about a high GPA counterbalancing a low GMAT is true to an extent, I don't think you can safely say you've addressed the issue. Unfortunately, a 640 is below the lower end of the GMAT range for the schools you listed, so it really would be a far stretch. If you could get that score within the range, then you can argue that your GPA is an indicator of your strong academics. I think you would need about a 680 to even begin that approach.
Good luck!
Daniel Richards
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