R.I. Gen. Laws § 28-7-37
Complaints, orders, and other process and papers of the board, its member, agent, or agency, may be served either personally or by registered or certified mail or by telegraph or by leaving a copy thereof at the principal office or place of business of the person required to be served. The verified return by the individual serving the process setting forth the manner of the service shall be proof of the service, and the return post office receipt or telegraph receipt when registered or certified and mailed or telegraphed shall be proof of service of the process. Witnesses summoned before the board, its member, agent, or agency shall be paid the same fees and mileage that are paid witnesses in the courts of this state, and witnesses whose depositions are taken and the person taking the depositions shall severally be entitled to the same fees as are paid for like services in the courts of this state.
R.I. Gen. Laws § 28-7-37