If it is (1) a relatively inexpensive chip, and (2) a sturdy casino chip that will hardly ever break in the mail, I would sandwich it between some cardboard (like from a cereal box, like Cheerios), tape it to a paper and send it off as a First Class International LETTER, plus a 21-cent surcharge. Make sure it is not more than 1/4 inch thick.

Rates:

Robert