A Doll's House clearly contains both feminist and Marxist themes, which intersect from the very beginning. As soon as Nora returns home at the beginning of act 1, she calls to Torvald to show him what she has bought. Her husband responds,
Bought, did you say? All these things? Has my little spendthrift been wasting money again?
Torvald's treatment of Nora as his child-wife is inextricably linked with his economic power. Within the home, he is both patriarchally and financially dominant. Outside the domestic sphere, however, Torvald has himself been caught up in the desperate struggle for economic security until he reached his current position at the bank. The other major characters in the play, Krogstad and Kristine, have been similarly plagued with financial insecurity.
When she leaves Torvald, Nora complains that her father handed her over to him as a piece of property. In abandoning him, she rejects both his authority as a husband and the economic security with which he provides her. In both feminist and economic terms, therefore, Nora's position at the end of the play reverses her position at the beginning.
A good thesis statement will make use of the intersection between feminism and Marxism in A Doll's House. For instance, you might say something like the following:
In A Doll's House, Ibsen shows how patriarchy is reinforced by Capitalist economics.
Another way of exploring similar issues would be to use a thesis statement along the following lines:
Nora has to abandon her economic and social outlook before she can leave her husband.