I'm just passing through.
(I'm here for) on business.
(I'm here for) Sightseeing.
Are you here for business or pleasure?
What's the purpose of your stay?
What's the purpose of your visit?
You'll want to get your passport renewed.
Can I see your passport and immigration form, please?
Here you are.
Here is my passport.
May I see your passport(, please)?
Let me see your passport(, please)?