The words thus and hence are both formal ways saying ‘as a result’. In formal texts, it is often suggested to use them slightly differently. Thus is used to indicate a conclusion about something that has happened in the past, while hence is used to indicate something that will happen in the future.
Profits were higher last quater; thus, everyone got a raise. ⇒ The raise already happened.
Profits were higher last quarter; hence, everyone is expecting a raise. ⇒ The raise hasn’t happened yet.