I agree that I can't think of an example of Sir Thomas laughing but I do believe JA pokes fun at him when: "Some one was talking there in a very loud accent; he did not know the voice—more than talking—almost hallooing. He stepped to the door, rejoicing at that moment in having the means of immediate communication, and, opening it, found himself on the stage of a theatre, and opposed to a ranting young man, who appeared likely to knock him down backwards. At the very moment of Yates perceiving Sir Thomas, and giving perhaps the very best start he had ever given in the whole course of his rehearsals, Tom Bertram entered at the other end of the room; and never had he found greater difficulty in keeping his countenance. His father’s looks of solemnity and amazement on this his first appearance on any stage..."