Here's how you write "Happy birthday" in Korean:
생일 축하합니다 (saeng-il chuk-ha-ham-ni-da)
This is the formal and polite way to say "Happy birthday" in Korean.
Here are some other options for saying "Happy birthday" in Korean, depending on the situation:
* 생일 축하해 (saeng-il chuk-ha-hae): This is a more informal and casual way to say "Happy birthday."
* 생일 잘 보내세요 (saeng-il jal bo-nae-se-yo): This means "Have a happy birthday."
* 생일 많이 축하해 (saeng-il mani chuk-ha-hae): This means "Happy birthday, and many happy returns."