You will have to ask the person on E-Bay, some will ship overseas some will not.
If you have it sent to your home and someone forwards it to you, they can check with their local DHL or FedEx and be sure of the price. But you will be paying double, to your home and then to Thailand.
Two years ago I had a bottle of medicine sent to me by FedEx and it cost me $21.00 U.S.