Uma Thurman's Custody Battle With Arpad

Uma Thurman's baby daddy doesn't deserve more visitation with their daughter -- because she says he's been a flaky father who has rarely seen the girl.

Sources connected to the case tell TMZ ... when she and ex-fiance Arpad Busson head to court in a few months, Uma will argue Arpad cancels his scheduled time to see their 4-year-old "7 times out of 10."

We're told Arpad is the one who's asking the judge for more time, but our sources say these are just "bullying tactics." Our sources say he gets a significant amount of custodial time currently, yet doesn't come close to taking advantage of it.

Sources say Uma wants to co-parent with Arpad, but only if the agreement is healthy for the whole family.

We're told when it comes to sharing custody, either she or a nanny has to take the child to London or the Bahamas, where he lives, because he won't take the time to pick her up.

On a separate note ... we're told Arpad wants Uma's engagement ring back. But she's gonna fight it because she claims it was gifted outright after the engagement was cancelled.