In order to construct a thesis statement for an essay analyzing this poem, you must first brainstorm and pre-write ideas for what you are going to write about. Remember, a thesis statement is one or two sentences giving the overall purpose of your paper. Until you decide what your purpose is, you cannot create a thesis.
That said, consider a few things that will help you begin. First, a poetry analysis should not simply be a summary of the poem. Consider that the general idea behind this poem is a man who is trying to persuade a woman to make love to him. The poem is a conversation but there is only one speaker. The man is creating the argument on both sides. It is a subtly witty poem; the humor is very tongue in cheek (meaning, ironic and not meant to be taken literally).
Keeping the purpose and message of the poem in mind, you should brainstorm and analyze which poetic techniques the author makes use of in order to portray this message. Some ideas to consider are: structure (stanzas, lines, rhyme scheme, rhythm), diction or figures of speech, tone and irony, and point of view. If this is a 5 paragraph essay, you need only analyze 3 major techniques.
Once you have taken the time to pre-write for this essay, your thesis statement will be comprised of the overall purpose of your essay (what you seek to prove) and the three avenues through which you plan to prove it (the poetic elements you choose to analyze).