This is a very tough case.
Copyright Law exists in order to further the useful arts by balancing the needs of the producer and the needs of the public. Let's look beyond the cheap shots that have already begun to permetate this thread and discuss in those terms.
Basically, this ruling amounts to telling wiley and sons (the producers) that they cannot reliably price discriminate for foreign markets. you might say "so what? tough cookies." but let's think about that for a moment.
basically, wiley has two choices at what price to set the textbooks at in thailand -
Price A - low price that thais can afford.
Price B - USA price or near to it
with price A, they can engage in fair competition in the thai market and earn a fair profit. at this price, they dont have too much to fear from piracy.
with price B, they can expect to sell few copies as piracy will be rampant. as it is highly unlikely that this is at the profit maximizing price, their profits will be lower.
this ruling basically compels them to either sell in thailand (a presumably much smaller market than the usa) at a price closer to price B or to make economically useless changes to their textbooks to make them unsaleable in the USA, such as printing them only in the thai language. or, they can do even worse stuff like arguing for import tarriffs from thailand to the usa on books.
even worse, it prevents them from doing things like giving away their textbooks in africa at a loss.
and even then, if they have to price at price B in thailand, their unit cost goes up and presumably they might have to raise the prices of US textbooks. a lose-lose.
first sale doctrine is important, but i dont see why it must apply accross borders given that there are other legitimate considerations, including the need to educate globally.
i cant say that this is a bad ruling, as ive not read the rulings, but offhand this issue is far more complex and in need of serious thought than some are giving it credit for here.