I would go for a routing via BKK on TG. Award seat availability with M&M miles is generally much better for TG than for SQ or NZ (I think this reflects the fact that TG is still regarded by many as a second tier airline, especially compared to SQ -- which I think is an unfair judgment). I did FRA-BKK-AKL around Christmas, and TG still had award seats available where others were already completely sold out of revenue seats. For connections, the new BKK airport is great. I especially enjoyed the Royal Spa where you could bridge the time between flights with an authentic Thai massage (for USD 15 per hour).