Using e^{+}e^{-} annihilation data corresponding to a total integrated luminosity of 7.33 fb^{-1} collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we provide the first amplitude analysis and absolute branching fraction measurement of the hadronic decay D_{s}^{+}→K_{S}^{0}K_{L}^{0}π^{+}. The branching fraction of D_{s}^{+}→K_{S}^{0}K_{L}^{0}π^{+} is determined to be (1.86±0.06_{stat}±0.03_{syst})%. Combining the B[D_{s}^{+}→ϕ(→K_{S}^{0}K_{L}^{0})π^{+}] obtained in this Letter and the world average of B[D_{s}^{+}→ϕ(→K^{+}K^{-})π^{+}], we measure the relative branching fraction B(ϕ→K_{S}^{0}K_{L}^{0})/B(ϕ→K^{+}K^{-})=(0.593±0.023_{stat}±0.014_{syst}±0.016_{ϕπ}), where the third error is due to the uncertainty of the B(D_{s}^{+}→ϕπ^{+},ϕ→K^{+}K^{-}). Our result deviates from the Particle Data Group value by more than 3σ. Furthermore, the asymmetry of the branching fractions of D_{s}^{+}→K_{S}^{0}K^{*}(892)^{+} and D_{s}^{+}→K_{L}^{0}K^{*}(892)^{+}, ({B[D_{s}^{+}→K_{S}^{0}K^{*}(892)^{+}]-B[D_{s}^{+}→K_{L}^{0}K^{*}(892)^{+}]}/{B[D_{s}^{+}→K_{S}^{0}K^{*}(892)^{+}]+B[D_{s}^{+}→K_{L}^{0}K^{*}(892)^{+}]}), is determined to be (-14.5±5.1_{stat}±1.8_{syst})%.