G is the gate voltage,
S is the Source electrode
D is the Drain one
when Vgs is greater than Vt, it is turned on
Vgs below 0 turn off.
Be aware the spice model only represent the typ. threshold voltage. Because the Xfab has different manufacture processes in their foundries (not identical as Intel or ST did) - Your HV MOS is manufactured in Malaysia not in Erfurt Germany. The technology is premature and cannot withstand high power, getting hot once turned on (cost is high as well). Vt is reduced with temperature, when the HVMOS is hot, Vth falls below 0.95V