To undergo lasik operation, does a person's cornea have to be 545 microns thickness, yes?

Not exactly. 545 microns is about the thickness of the average cornea. Certainly patients with corneas thinner than 545 microns can have lasik depending on their prescriptions and the health of their corneas.
Not exactly. The amount of corneal thickness required to do lasik is dependent on the amount of correction you require. Your eye surgeon will determine this.