Passport Renewal Application For Expatriate Staff From China

I want to know regarding the passport renewal application. Appreciate if you can answer below my question:-

1) For renewal, is it need to make appointment first or can walk in?

2) Is it have minimum period to do the renewal?

3) I have 1 expatriate staff from china, his employment pass is due on 26/03/2025 and his passport will be expired on 03/05/2025, so when he can come for renew his passport?