Dear irishguy,
I did a test booking after your reply to travel J class same dates (next week)
84.000THB or approx 2270 euro.

I have not yet received offer for both return segments, experflyer shows both flights J9, C8, D7, I7, but I doubt offer will be under 600 euro.

Thus again 4x600 = 2400 euro on top of eco fare paid, that's undeniable more expensive than buying a biz ticket return from the start.

Yes, I missed out on the 1550 euro and 1700 promotion because of family issues, not wanting to pay 2000+ I booked eco booking class N ticket, I am happy with that, just finding QR offer to be more expensive than normal ticket.

I will let you know the offer on the return segments but at 600+ I am not buying...

It might be nice for an eco passenger to try out biz on one segment to get the taste of J...