Based on the level of respect or formality, you can say "Can you say it again?" in Korean in 3 ways:

• Informal: dasi hanbeon malhae-julrae? (다시 한번 말해줄래?)
• Formal: dasi hanbeon malhae-jusigetsseoyo? (다시 한번 말씀해 주시겠어요?)
• Very formal: dasi hanbeon malsseumhae-jusigetsseumnikka? (다시 한번 말씀해 주시겠습니까?)