Let me tell you that it is not worth it to use your Amex to buy something online on overseas currency, even though it is a weekend. I did a amazon online transaction over a weekend thinking I will be rebated 5%, but turns out that the transaction date on my bill appeared as 3 days later (weekday) after the actual transaction date. My conversion charge also higher at 2.5% by Amex (actually I am not sure was it 2.5% or 2.5%+0.5%).
Whatever it was, you would be better off using your Maybank Master or Visa card for online overseas purchase. Unless you think 5x treatspoint is worth it (equivalent to about 2.5% also)

Gen.X Quote#13 ( Jun 3 2011) is true:
13. The 5% cash back on weekends (Saturdays and Sundays) for MBB 2 AMEX includes Petrol and is additional to the 5X Treats Points. However it is reported that some online transactions on weekends DO NOT earn the 5% cash back as it depends on the timing the merchant processes the transaction.

This post has been edited by kartz25: Sep 16 2011, 04:46 PM