I agree with the above; because of the short distance, it doesn't matter if you fly BKK>Khon Kaen in coach or Business, you're still only gonna get 500 miles.

This practice is contrary to the way most (if not all) US carriers calculate mileage. They apply the multiplier (usually 1.25 or 1.5) on the minimum (500) when the distance is less than 500.