Would the phrase "Won't you please help me?" be more polite than "Will you please help me?"? In the same way as the previous example, would negative interrogative sentences as asking a request/favor be polite more than interrogative ones?-- Strangely, no. The negative forms suggest that the speaker thinks s/he won't be helped; it expresses worry or frustration or anger.
I understand. Thank you so much. I wondered why the negative interrogative sentence "Won't you please, please help me?" is used in the lyric of Beatles' song, help!.