Even though this promotion started 24 May 2019, it just appeared recently in my mailbox, so perhaps they sent it out in batches to various groups of people.
Based on the T&Cs (see them here), you need to receive a SMS or electronic direct mail from OCBC to qualify. There’s no mention of the types of things you can spend on, so long as it’s foreign currency, which is pretty good since it’s the June holidays and most people would be away on travels! The basic earn rate for foreign currency is 2.4 mpd for foreign spend, so essentially you get 1 mpd more during this promotion!
Do take note of the cap of $5000 spend. The additional miles will be credited to your Card account by 31 July 2019.
In addition, do not forget about the free limousine ride that you can claim once you spend $1500 in foreign currency. You can earn up to two free limousine transfers per month (to/fro airport) and every ride earned is valid for three months.
With regards to the booking of limousine, SMS notifications will be sent to the Main/Principal Cardmember’s bank registered mobile phone informing him/her of the award by the 2nd week of the following month where Cardmember meets the eligible spend requirement. A reservation code will also be availed in the SMS. The Cardmember should share this reservation code with VOYAGE Exchange at point of reservation.