I thought I would also join the Tiger Haters fun club because of their online flight booking procedures. It is important to note that you cannot book a flight if 1) you don't key in your passport number and expiry date and 2)if your passport is expiring in six (6) months.
Q: Excuse me Tiger Airways, what if you have this ridiculously awesome promo fare that I want to book but my passport is expiring in 6 months? Can I put mock passport details and have it changed after I get my new passport, hopefully for free?
A: Fuck off.
Seriously. If you search the interwebz for answers, you will just end up very confused. Other people even said that a certain fee would be charged for passport amendments (!!!!). Some said it's free of charge but you need to wait laboriously to get through the hotline. In Manila, the phone agent even told my friend that changing of passport details is subject to management approval. Corporate evil whores.
I'm based in Singapore so Kin suggested that I call the hotline here to check if there's another option. I dialed +65 68084437 and braised myself for a 45-minute telephone muzak. Amazingly, a phone booking agent picked up (in under two minutes yey!) and breezily helped me amend the passport details FREE OF CHARGE. You just need to provide your itinerary reference number, birthday, old passport number (the one you keyed in when you booked the flight, very important!), new passport number, and new passport expiry date. Afterwards, they will resend via email your "correct" itinerary as proof that there's still hope in this world.
Have a safe flight! :)