No registration is required for this. The maximum bonus you can earn is 8,000 miles or S$1,000 spend per statement period (which may or may not be calendar month).
I know everyone is holding out for the Black Friday sales on Amazon in November. No worries, you can prepay your Black Friday balance by buying an Amazon Gift Card now.
The cap applies per card, not per account. What this means is that if you have both the Citibank Rewards Visa and MC you can get up to 16,000 miles per statement period (spending $1,000 each on the Visa and MC).
The downside of Citibank is that they make it difficult to pool your points for redemptions. I understand that if you dial in you can ask the CSO to pool your points so that you only pay one conversion fee but I’ve not tried this before.
If you need someone to mule your Amazon purchases back home, try AirFrov.