From now until 31 Mar 2020, you can earn 4 mpd on eligible spend when you use your DBS Altitude Card overseas. This promotion is valid for both the Visa and American Express versions of the card, subject to a minimum spend of S$2000 in equivalent foreign spending during the promotion period.
You must register first before you get to enjoy this promotion. Also, the promotion is only open to the first 5000 cardmembers who successfully register for the promotion. You will receive a confirmation once you successfully register yourself for the promotion.
Note that online flight and hotel transactions do not count, but most other transactions in foreign currency should count.
The 4 mpd earn rate comprises the base rate of 2 mpd, and a bonus 2 mpd. There is a cap of 14000 bonus miles for this promotion, which is equivalent of S$7000 worth of eligible spending. The bonus miles will be credited to you account in the form of DBS Points up to 90 days after 31 Mar 2020.
More information can be found here.