You can boost post on Facebook in multiple languages if you are using the same image or video for your ads in all the languages.

To boost a new post in multiple languages:

1. Select Settings at the top right of your business page.
2. In the General tab, scroll to Post in Multiple Languages and tick Allow people who manage this page to write posts in multiple languages. Choose Save Changes.
3. Compose an ad from your business page, then select Write post in another Language.
4. Choose the ad's Default language. The ad in the default language will be served to people who speak that language and are likely to be interested in your ad but don't speak one of the other languages you'll select.

5. Click Select and choose another language from the dropdown menu. You can ad as many languages as you like.

   Some of the available languages have an automatic translation feature. The auto-translated text can be edited.

6. Select an image or a video for all your ads. The same creative will be served in all your languages.
7. Choose Boost Post to publish your ads.

Your ad will now be served in multiple languages to people who are relevant to your business.

* Nguồn: Facebook