Why is Staley letter home so funny??

In his first letter, Stanley was lying. In his second letter Stanley is honest. His honesty is what is funny here. Stanley comes right out and tells her how awful the camp is. We can read Stanley's voice (personality) within his words.

In my last letter I lied to you, but the truth is I want to leave this camp as soon as possible. The living conditions here are terrible. We have to sleep in a small cot which smells like expired sour milk. The weather here is extremely scorching there is no shade here. There is also scarcity of water.