Piper Arrow pilot reported their left main landing gear collapsed during landing resulting in a runway excursion and damaged runway light.

Narrative

My girlfriend and I went flying in our piper Arrow III. The conditions on the field were VFR; light winds from the North; 10 mile visibility and a temperature of 26 degrees. During routine touch and goes I entered a downwind for runway XXL at 6800 ft. Abeam the landing point I configured the aircraft using the GUMPS callouts; Gas on fullest tank; Undercarriage down three green; Mixture set; Propeller full forward; Seatbelts on and secure. I also added 10 degrees of flaps followed by the Landing Checklist. On base turn; I increased to 25 degrees of flaps and slowed the aircraft to 70 knots and continued descent to about 6500 ft. After clearing final; I turned the aircraft to line up with center line; increased to final flaps of 40 degrees; slowed to final approach speed of 60-65 knots; and verified on glide path with the visual PAPI's. On short final; I glanced at the gear position indicator and verified 3 green lights. As we approached the round out and flare; I increased the pitch; decreased power and set the aircraft down in a normal manner.The aircraft attitude was standard Arrow III SOP. Upon touchdown I felt the aircraft sink to the left more than normal thinking is was a flat tire; so I added right aileron. I noticed the aileron was more than normal; so I glanced at the gear position indicator and noted the left main gear light was extinguished. At that point I recognized the Left Main Gear had collapsed; and looked at my airspeed which was decaying from about 45 knots. With no energy left available for attempt a go around; I added right rudder; right brake; full right aileron; and pulled the mixture to idle to decrease forward thrust as the aircraft began to pull left. I noted ahead the drop off and told my girlfriend to hold on as we left the pavement. The left wing was dragging at that point and struck a runway light. The aircraft went over the edge of the embankment and came to a stop. I immediately asked if my girlfriend was okay; which she was; then turned the electrical power off the aircraft until I could determine if there was a fire. Once I determined there was not a fire; I restored power; used the radio to inform ATC of the runway excursion. I informed them that we had a gear collapse; and went off the left side of Runway XXL somewhere after the 1000 ft markers. Additionally I told them souls on board and about 40 gallons of fuel remaining. I informed ATC we would be exiting the aircraft at the end of our conversation. I told my girlfriend to exit the aircraft and we left through the main fuselage door; then walked up to the side of the runway where we were met by airport operations and emergency services.