Sammer accused the team of being "lethargic" during a 2-0 win over Hannover a few weeks ago, earning a reprimand from club chairman Karl-Heinz Rummenigge for speaking out of turn.
While Sammer's intention was to keep last season's treble winners on their toes, Lahm says he should have gone about in another way it and not let off steam in public.
"He should have kept it internal," Lahm told the Die Zeit newspaper. "For us players, what the management say does not play such a big role. It's more important how they act within the club.
"A good coach and captain moderates, he doesn't dictate. Certainly not with the help of the public."
Lahm said Sammer still has a lot to learn if he wants to be a successful successor to current president Uli Hoeness, who developed a reputation for his outspoken nature, earning respect at the same time.
"It takes a while before you develop a feeling for when the right time comes for this kind of thing, and what tone you should take," added Lahm.
"You've got to be able to keep your emotions in check when the time comes to criticise.
"If the boss is too emotional, then he loses out in the end. He no longer has any credibility."
In spite of - or because of - Sammer's words, Bayern remain unbeaten in all competitions this season, apart form defeat in the German Supercup to Borussia Dortmund in pre-season.