A potential thesis statement that you might like to consider on the subject of human trafficking is as follows:

Despite their stated commitments, governments the world over have failed to get to grips with the growing problem of human trafficking. It's often the case that laws passed to deal with the problem have been too lax, or they haven't been properly enforced.

As with all thesis statements, you need to provide hard evidence to back it up. In this particular case, there is plenty of evidence provided by many different sources, such as pressure groups, charities, and independent commissions.

All of these groups routinely provide detailed research on the failures of governments across the world to deal with the growing problem of human trafficking and the dire consequences it has for some of the world's poorest and most vulnerable people.

In developing this thesis, it's a good idea to answer the question as to why governments don't seem to be taking the problem of human trafficking as seriously as they should. You could look at the domestic constraints within which governments operate, such as public opinion, which is invariably hostile to the victims of human trafficking, no matter how much they've suffered.

You could also look at the way in which countries the world over actually benefit economically from the supply of cheap labor provided by the activities of human traffickers.

When crafting a thesis statement for your essay, think about what in particular interests you about the topic of human trafficking. There are many angles from which you could approach this topic. Perhaps you would like to write about the ways that different parts of society are complicit, intentionally or not, in human trafficking. Maybe it could be something about how certain populations are more susceptible to human trafficking than others. You could even make the focus of your essay about possible solutions to the problem of human trafficking. Whatever it is that you choose, your focus should be on something that you are interested in diving deeper into.

After you pick your approach to the topic, start doing some research into it. As you do so, look for something to focus your paper on that is provable through evidence. A proper thesis statement should make a compelling and interesting point that will be backed up through evidence and rational argument over the course of your paper. If you find that you are not finding enough evidence to back up the thesis you want to make, this is a good sign that you may need to change your approach.

Your thesis statement itself should come somewhere near the end of your introductory paragraph. Make it clear and unambiguous. Anyone who reads your essay should be able to easily identify what your thesis is. Once you lay out your argument with your thesis statement, use the body paragraphs of the essay to provide evidence to support it.

Many teachers often want a classic five-paragraph essay, so it often helps to create a thesis that has three main points. A thesis should present a defendable position, and you will support this position with evidence in the body paragraphs of your essay.

There are numerous angles that you could use to examine the topic of human trafficking. You could examine exactly who is exploited with a thesis that looks something like this:

Human trafficking exploits children by forcing them into commercial sex, victimizes adults who are forced to various laborious work, and abuses children and adults who are forced to work to repay debts.

Those three key points will become your three body paragraphs. In each, you will provide more information about each of those groups, including data to show how and where this happens across the world.

You might also consider the effects of human trafficking on society. That thesis might look something like this:

Human trafficking has devastating effects on society, including the devaluation of women in societies, the decreased physical and mental health among those who are trafficked, and an increased population of organized criminal groups.

You might also examine which populations are most at risk of being trafficked:

Human trafficking targets some populations with greater frequency, including the poor, the socially excluded, and the weak.

You could then provide research that demonstrates how each of these groups becomes more vulnerable to human traffickers and conclude with strategies that societies can employ to protect its most vulnerable members.

I hope this gives you some ideas as you construct a thesis regarding this worthwhile topic. Good luck!

The thesis statement is a one or two sentence statement which sets the tone of the paper and gives the reader an overview of the content of the paper.
I tend to construct thesis statements in a subject-description-triple content model. 

Human trafficking (subject) is a growing evil (description) destroying communities (content 1), expanding gang activity (content 2) and robbing the innocence of the world's youth (content 3).

The model lets the reader know the subject of the paper, your view of it and the supporting arguments you plan on providing in the paper.  The rule of three makes a paper easy to read and provides enough content for the discussion.  Sub-sections can always be introduced to address additional areas of concern.

There are many aspects of human trafficking that can be addressed in a paper.  The first step to writing the thesis statement is to decide what areas of human trafficking you want to focus.  Areas you may want to include loss of innocence, financial cost, slavery, sexual abuse, emotional scars, gang activity, degradation of communities, judicial burden, or the difficulty in tracing missing persons.