Kevin Federline ain’t sweating it -- firing back at Sam Asghari ’s "professional dad" dig ... and flipping it as a straight-up compliment instead of shade.

Catch our clip -- Kevin shrugs off Britney ’s ex-hubby’s jab ... saying, end of the day, being a "professional dad" is exactly what every father should aim for. Gallery Launch Gallery Getty

Reminder -- Kevin’s held full legal and physical custody of his and Britney’s boys -- Sean Preston and Jayden James -- since 2008 … and he’s been a steady rock in their lives ever since.

The whole convo sparked as Kevin preps to drop his memoir "You Thought You Knew" -- where he’s spilling his side of life with Britney in his own words. Play video content

Sam was really just reacting to the tell-all ... joking it c

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