  The problem of determining the radiation reaction force experienced by a
scalar charge moving in flat spacetime is investigated. A consistent
renormalization procedure is used, which exploits the Poincar\'e invariance of
the theory. Radiative parts of Noether quantities carried by massive scalar
field are extracted. Energy-momentum and angular momentum balance equations
yield Harish-Chandra equation of motion of radiating charge under the influence
of an external force. This equation includes effect of particle's own field.
The self force produces a time-changing inertial mass.
