Yannick Ferreira Carrasco scored twice inside the first 10 minutes as Monaco flew out of the blocks, seemingly on course for three points against a team who had previously taken just five points this season.
However, the hosts - with Herve Renard in charge for the first time after his move from Zambia - hit back to ensure a share of the spoils with goals from Cedric Bakambu and Joseph Lopy.
The result saw Monaco drop two points behind Paris St Germain at the top of the table.
Ranieri, though, was not annoyed with his team, but instead pinpointed the reason for their lapse, something which can be improved.
He told reporters: "Am I angry ? No! Football is a wonderful sport.
"We quickly scored two great goals , and afterwards we have forgotten concentration but Sochaux made the game I expected."
Neither would Ranieri use the excuse of the players being tired following their international exertions, saying: "We have not cracked physically. Maybe after the second goal, it was believed that the game was over, but it was not."
Of losing top spot, the former Chelsea boss said: "No, this is not a problem. You just need to improve game by game. "
Midfielder Geoffrey Kondogbia added: "We were not complacent. We just conceded two avoidable goals and that is unfortunate."