Ads may load on your site in a non-English language if you or a reader match the criteria for the campaign. Ads are targeted on an individual basis and even if the language of the ad is not spoken by the user, other internet habits can qualify a user to see the campaign. Habits such as visiting a site originally published in a foreign language that was translated into English or searching for a word in another language could both be tracked and retargeted for such a campaign.
Non-English spoken ads will be less common, but if they do appear, the compensation will be on par with English campaigns.