Can a foreign resident in Korea claim a basic deduction for a spouse residing in their home country?

Yes, You Can!

Even if the spouse does not live together in the country, if the spouse's annual income is less than 1 million won, a basic deduction can be claimed. Documents that can confirm the relationship between the taxpayer and the spouse (e.g., family relationship certificate, marriage certificate, or similar documents issued abroad) and an income certificate from a foreign authority that verifies the spouse's income should be submitted as supporting documents.