Jo Koy is recalling the moment his international flight needed to make an emergency landing after an electrical fire filled the cabin with smoke … and he says his son helped his family stay calm with a perfectly timed joke.

We got the comedian at LAX and he told us about his scary situation on his most recent flight … a long journey from the Philippines to Los Angeles that required an unplanned stop in Japan early Thursday.

Jo says he was trying to sleep when he started noticing smoke and heard flight crew running around, slamming overhead compartments … and he knew something was wrong.