Apple in fact officially documents multiple ways for you to be able to empty account balance, it just doesn't mention them in the document most frequently referred to when the question about emptying balance arises. However, I have noticed that posting my usual, conscientiously complete response is frequently considered to exceed what is regarded to be a good response to your question. In the interest of full disclosure I here list all three ways I have found, should you wish to explore others:
Read this support article for information about requirements for changing your Apple ID country or region --> Change your Apple ID country or region - Apple Support . It only mentions a single way to empty account balance, but there are actually three valid ways, all officially documented by Apple in other support articles. Only mentioning the single method where you give your money to Apple appears to be preferred in replies to questions like yours, but in the interest of full disclosure I list all three ways here should you wish to explore others:
1) Spend it:
If your store credit is less than the cost of a single item and you still have a valid payment method such as a credit card for your old country, you can use the payment method to make up the difference in the cost of an item ( How apps, content, and subscriptions from Apple are billed - Apple Support ). Perhaps buy something such as a music track which you can download and also keep a backup copy. Remember that anything purchased may not be available for re-download in another country but as long as you have your own copy you will always have it.
2) Ask Apple to keep it:
From Change your Apple ID country or region - Apple Support you can use one of these methods to ask Apple to remove the balance and keep it:
● Click here --> Choose your country or region - Official Apple Support Select your country, then a product such as billing. If you do not see your country, see if there is an "other" listing for that region. If you don't see an option that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
● Call Apple Support --> Contact Apple for support and service - Apple Support
3) The article: Check your Apple Account balance - Apple Support has a section titled, "If you have an Apple Account balance that you can't use". You can ask for a refund, but only under very specific conditions and locations to the extent that I have yet to see anybody respond saying they have used this method. Still, the document itself says it's an option for some if they have "unused Apple Account balance".
