Yes, you can. BookBeat works all around the world. Just remember that if you want to continue using BookBeat after your gift card period has run out, you will have to be located in the country the gift card was bought from or have a payment method from this country available.
Gift cards are only available for the following markets and have to be bought on the respective website: Austria, Belgium, Denmark, Finland, France, Germany, Italy, Netherlands, Norway, Poland, Spain, Sweden, Switzerland, United Kingdom
Gift cards are not transferable between markets.