A thesis statement about Ralph could center on how Ralph represents civilization in the story.
A thesis statement is an argument. If you are writing about a character, you will want to argue something about that character. Ralph does represent order and civilization. A sample thesis statement could be this one.
In Lord of the Flies, Golding represents civilization through the character of Ralph, because Ralph has an orderly government compared to Jack’s savagery.
At the beginning of the story, Ralph is described in almost perfect terms. He is “fair haired” and tall, and in good shape. He is also “startled” at the thought of there being no adults and responds “solemnly” at first, but then is “delighted” to realize that no one is there to tell him what to do (ch 1). This eventually turns into the realization that someone has to be the leader, and Ralph blows the conch, symbolically bringing order to the island of boys.
The conch was silent, a gleaming tusk; Ralph’s face was dark with breathlessness and the air over the island was full of bird-clamor and echoes ringing. (ch 1)
Although Ralph is not the one who gets the idea to blow the conch, he does listen to Piggy when he tells him that he can use it to call everyone else. Since the conch is used by Ralph, Ralph becomes de-facto leader.
Ralph’s unquestioned leadership does not last long, and soon Jack questions it. Jack does not want to be a leader to get things done, he wants to be a leader to make people do what he says.
We’ll have rules!” he cried excitedly. “Lots of rules! Then when anyone breaks ’em–” (ch 2).
Jack’s insistence on rules for the sake of rules and punishments for those who break them demonstrates that he just wants to hurt people, not lead them. Jack is a bully, while Ralph is more considerate.
At the end of the story, Golding reinforces the idea that Jack represents civilization when he is the first to be rescued.
[With] filthy body, matted hair, and unwiped nose, Ralph wept for the end of innocence, the darkness of man’s heart, and the fall through the air of the true, wise friend called Piggy. (ch 9)
Ralph recognizes what has happened on the island, and he knows he will never be the same. His innocence is not just lost, it can never return because he has seen the savage side of human nature and the worst that people can do.