ABSTRACT Additive manufacturing of lightweight structures encounters the problem of producing parts less than certain thickness. For example, walls built using a single beam pass at each layer, also known as ultrathin walls [1], tend to have a spoiled morphology due to inhomogeneous heat and mass transfer, causing the hydrodynamic instability of the melt pool [2]. Spot melting is attracting research attention due to its potential to gain more control over microstructure and mechanical properties in powder bed fusion, leading to increased material quality and reproducibility [3, 4]. Optimization of spot melting parameters, in particular, the spot sequence, could improve the temperature field homogeneity [5]. Here we present a simulation study on how spot melting could help improve the morphology and control the microstructure of ultrathin walls built from Inconel 625. We use KiSSAM simulation software for additive manufacturing [6] as it is a high-performance mesoscale code, capable of simulating multilayer problems in reasonable time, taking into account all necessary physical effects [7]. Simulation results show that utilizing the spot melting sequence helps to significantly reduce the instability of the melt pool during the wall build, to improve the wall morphology, and to provide a more homogeneous grain structure. [1] Lu et al., Mater. Sci. Eng. A, 2022, 835, 142652. [2] Korneev et al., Addit. Manuf., 2023, 74, 103705. [3] Nandwana & Yousub, Mater. Today Commun., 2020, 24, 100962. [4] Lee et al., Proc. 28th Solid Freeform Fabrication Symp., 2017. [5] Kupfer, Breuning & Markl, Addit. Manuf., 2024, 91, 104321. [6] Zakirov et al., Prog. Addit. Manuf., 2024, 9(5), 1491–1508. [7] Zakirov et al., Addit. Manuf., 2020, 35, 101236.