Other than whats printed on the label how can i know 100% that it is imported.

As an example, Premium Australian Rib Eye sold at foodland etc etc.

Well unless you are buying it off the back of somebody's truck, suffice to say Foodland, Villa and the like would not be re-labeling their meat for a few baht.

As for the steak in question, if you throw it on the bbq and jumps off the grill and yells "What are doing pommie, that's hot mate" then it's mostly Australian.