if you booked directly with SQ, your e-ticket should show the class booked. We returned from Sweden a couple of days ago, all 6 flights booked with and ticketed by SQ - sorry, don't know how to post the image here as it is different to the one you've included (which looks like a VA produced itinerary?), but the e-ticket from SQ shows:

Flight Details, then underneath that Ticket Number: xxxxxxxxxxxx
then for each flight:
On left-hand side of page: SQ XXX Operated by Singapore Airlines (or whoever)
Right-hand side of page: Economy Class and the fare class in brackets e.g. on ours it's either (H) or (W).
Details of the flight are listed underneath.