Thomas Paine National Historical Association
If by “socialist” we mean a state-supported welfare system to ensure the poor and working poor lead comfortable lives, then yes. Paine supported a social welfare state.
If by “socialist” we mean that wealth is produced by the working classes (in his day the farmers and the mechanics) and that they should reap the benefits of that wealth, then yes as well. (Paine had a labor-theory of value).
But if by “socialist” we mean the definition it was to gain some 20-30 years after his death, ie. that the working classes control the means of production through the state, then probably not.
Those ideas and even the language around them had not come into use during Paine’s lifetime. In his era capitalist forces were just taking shape, and he did not foresee some aspects of that. In reference to “socialism” in that light, he would have no clear grasp of the issues involved.
He did support the program of Babeuf in the French Revolution, but opposed his methods. (The word “communism” was coined by Goodwyn Barmby in a conversation with those he described as the “disciples of Babeuf”.) So all in all, he seems to have supported many of the tenets of what people later referred to as “socialism.”
http://thomaspaine.org/aboutpaine/was-thomas-paine-a-socialist.html