I'm going to confuse things here. I have a reward flight booked through BMI and I can see my booking on Thai's website. I just entered the main PNR for all of my flights and surname - appears no problem.
However I can also see my booking on checkmytrip.com and I see that at the bottom of my booking on the Thai website it says you can look on checkmytrip.com. So it coould be a booking system issue.