Surface mount thermistor practices
If you want it primarily coupled to the housing, eliminate the any copper pour thermal connections to the rest of the PCB, use thin conductors (perhaps in serpentine pattern) and consider slotting the board to further isolate the sensor.
You can also insulate the PCB around the sensor to attempt to isolate it from the air in the enclosure. Something like self-adhesive polyurethane foam tape (but be careful that the electrical properties of the adhesive do not come into play).