Article critiques should always discuss the author's main points, how they argue those points and any weaknesses in the argument. A thesis statement for such a critique should encompass your general response to the main arguments in the original article and can also suggest some further insights you would give to the main article's premise. Writing a few rough drafts of the thesis statement will help you refine the main argument of your article critique.
Note all the main points you will bring up in the article critique on a sheet of scratch paper. For example: the original author's main point, their main emphases in the article, and the strengths and the weaknesses of the article. These points will comprise the main points you will be making in the article and the potential ideas that will make up your thesis statement.
Connect the main points from Step 1 into your concise argument or response regarding the article. For example, the author may be talking about issues with dyslexia, which adds to the literature on the topic, but they do not problematize a couple of their sources. A possible conclusion you would draw from these factors would be that the article is helpful in building on earlier authors, but fails to complete the argument because of weak sources.
Practice writing sentences that reflect your ideas from Step 2. For example, "This article adds valuable emphasis to work done on the level of stress experienced by children with dyslexia, although the author could have used stronger sources." This statement could be made into more than one sentence if there is too much information for a single sentence. The thesis statement should tell the reader where you are going with your response to the critique, and open up the rest of the critique.
Place the thesis statement in the first paragraph of the article critique. Often, the thesis will come near the end of the first paragraph.