Regas have also no ground wire. It is internally connected between the dins on the tonearm and I believe that it's the case with your Thorens.
No Ground on Thorens TD 145 MKII + some questions
I purchased a real nice Thorens Turntable for my 13 year old son's system. (Mini Me) I unpacked it and no ground wire. I hooked it up and all is fine , it sounds great. No Hum or problems. I have never seen a turntable without a ground wire. The previous turntable in this system was unusable without the ground wire connected. I opened the botom and noticed a wire running across the bottom of the inside, with no provision to attach a ground wire. Is this normal on this model ? Should I run a ground wire to this wire or leave well enough alone? Also I could not get the inner platter to come off , I wanted to lubricate the spindle. Is there a trick to getting this part off? Thanks !