To find the Mongol alarm without raising the alarm in Shadow of the Samurai in the Ghost of Tsushima go behind the wagon to the left and assassinate the guard.

Keep going behind the house and go across the street into the next house and assassinate the guard in that house.

Jump out of the window and wait for the guard to pass by and assassinate it.

Go around the house on the other side of the street and assassinate the Mongol near the alarm.