Why did Theroux refer to Laos as "America's expensive practical joke"?

Theroux found the city of Bangkok to be very uncomfortable, hot, and loud, and therefore, unfit to live in. However, the city seemed to thrive on offering services to tourists and therefore seemed to exist solely for the pleasure of people passing through. For instance, despite the fact that American soldiers no longer visited as the war in Vietnam was winding down, the city still maintained its massage parlor and sex services economy.