Study of the decay <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>D</mml:mi><mml:mi>s</mml:mi><mml:mo>+</mml:mo></mml:msubsup><mml:mo stretchy="false">→</mml:mo><mml:msubsup><mml:mi>K</mml:mi><mml:mi>S</mml:mi><mml:mn>0</mml:mn></mml:msubsup><mml:msubsup><mml:mi>K</mml:mi><mml:mi>S</mml:mi><mml:mn>0</mml:mn></mml:msubsup><mml:msup><mml:mi>π</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:math> and observation of an isovector partner to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>f</mml:mi><mml:mn>0</mml:mn></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:mn>1710</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math>

Using ${e}^{+}{e}^{\ensuremath{-}}$ annihilation data corresponding to a total integrated luminosity of $6.32\text{ }\text{ }\mathrm{f}{\mathrm{b}}^{\ensuremath{-}1}$ collected at center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay ${D}_{s}^{+}\ensuremath{\rightarrow}{K}_{S}^{0}{K}_{S}^{0}{\ensuremath{\pi}}^{+}$ for the first time. An enhancement is observed in the ${K}_{S}^{0}{K}_{S}^{0}$ mass spectrum near $1.7\text{ }\text{ }\mathrm{GeV}/{c}^{2}$, which was not seen in ${D}_{s}^{+}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ in an earlier work, implying the existence of an isospin one partner of the ${f}_{0}(1710)$. The branching fraction of the decay ${D}_{s}^{+}\ensuremath{\rightarrow}{K}_{S}^{0}{K}_{S}^{0}{\ensuremath{\pi}}^{+}$ is determined to be $\mathcal{B}({D}_{s}^{+}\ensuremath{\rightarrow}{K}_{S}^{0}{K}_{S}^{0}{\ensuremath{\pi}}^{+})=(0.68\ifmmode\pm\else\textpm\fi{}0.0{4}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.0{1}_{\mathrm{syst}})%$.