If you've made advances to him, then he's probably well aware that you're gay.
And don't come out to him just because you are hoping for a relationship; come out to him because you want to share with him this personal detail about yourself.
Having said that, it will be a good idea to clear the air. Better that you know, than that you pine for him, if it doesn't work out. And of course if it does, then yay! But take this one step at a time. Tell him, in person, that you are gay. And make it clear to him that his friendship is very important to you.
And then see what happens. He may feel freer in your country than in his own, and something might develop. Or maybe he's closeted no matter where he goes. Or maybe he gets uncomfortable and the friendship ends. Or maybe he's 100% straight and you stay pals but nothing else happens.
So start with a conversation. No big feelings revelations. No asking/suggesting a relationship.
"I just want you to know that I am a gay man. And I also want you to know that your friendship means a great deal to me. This is why I feel so comfortable telling you, and making it clear."
See what happens.