Accused subway saboteur Isaiah Thompson — who authorities say has caused more than 700 commute-crushing delays since March by pulling train brakes — was arrested again on Friday for yet another transit-related incident, police said.

Thompson, 23, turned himself into police following his latest suspected stunt on Wednesday, where he was seen “subway surfing” outside a northbound 5 train between the Brooklyn Bridge City Hall and Union Square stops, cops said.

Witnesses at Union Square alerted authorities, prompting Thompson to flee into the subway tunnel, police said.

He turned himself in to the 6th Precinct on Friday night. He was charged with reckless endangerment and criminal trespass.

Friday marks Thompson’s 18th arrest for subway-related offenses. He was indicted following his last May 23 arrest for allegedly pulling a subway brake on a northbound No. 2 train near 14th Street in Manhattan.

The compulsive brake-yanker had been free on $10,000 bond before Friday’s arrest.