A speech thesis needs to provide more than just the expression of a viewpoint or a simple statement of facts backed up by evidence. The idea of a speech thesis is to elicit a certain response in your audience, to engage them and encourage them to see the issue through your eyes. Before giving a speech thesis, have a clear idea of the response you want from your audience and the means by which you are going to achieve it.
One of the most important factors of a speech thesis is to show your credibility as a speaker. Anyone can have an opinion on any subject, but to give a speech thesis, your audience will want to know that you are knowledgeable in your field. You can demonstrate your expertise by quoting sources of books and papers you have read in your speech thesis or recent statistics related to your subject matter. Quoting an opinion without demonstrating knowledge is likely to leave your audience skeptical.
Your position in a speech thesis should be clear and unambiguous. For instance, if you plan to speak on a sensitive subject such as abortion, it's not enough to see the issues from both a liberal, free choice position and a religious perspective. The words of your speech thesis must be clear and understandable to the audience. If you appear undecided or lack assertion in your thesis statement, it will appear weak and poorly thought out.
A speech thesis should not contain all the details of your argument. A brief summary of the most convincing areas of your argument will suffice. It helps if the issue is contemporary and you can persuade the audience that the issue at hand has a quantifiable effect on their lives. For instance, a thesis on the rising price of gasoline will probably yield more interest than one on the presence of black holes in the universe. Black holes are a fascinating area of research, but do not affect people on a day-to-day basis.