Thalassemia minor and low hemoglobin?

With the proper medical clearance, it is entirely reasonable to do even significant elective / cosmetic surgical procedures on patients with many medical conditions. It sounds like you are doing everything correctly. Assuming your internist/hematologist clears you for the procedure and is comfortable with your blood count, I see no reason to forgo or delay your operation. If there is any question, your surgeon should have a discussion about the matter with your internist. Remember…a good surgeon is a physician first and should have a clear understanding of any medical condition their patient has before operating on them.It's critical that you seek the advice of a surgeon who is certified by the American Board of Plastic Surgery and has extensive experience with tummy tucks.
I wish you the best,
Dr. Gabbay.

I would suggest that you discuss with your plastic surgeon at your Pre Op your concerns and certainly you should follow up and obtain a medical clearance from you hematologist. Many times, procedures can be performed with a lower Hgb, as long as it is monitored. 
Best of Luck

Despite being a pretty "big" operation, blood loss during a tummy tuck is usually pretty low.  About 95% of the surgery is done with the Bovie cautery (basically an electric scalpel which seals blood vessels as it goes).  If your slightly low blood count is a chronic condition, your body has adapted to it and it would not be a contraindication for surgery.  I am sure your surgeon will be extra cautious and will do everything to minimize blood loss.