NONE 20260327110634969 wseas/wseas content-registration-form+ja@crossref.org content-registration-form WSEAS TRANSACTIONS ON BUSINESS AND ECONOMICS 1109-9526 2224-2899 Kanoktip Kotsamran Department of General Science, Faculty of Science and Engineering, Kasetsart University, Muang, Sakon Nakhon, THAILAND Soontorn Boonta Department of General Science, Faculty of Science and Engineering, Kasetsart University, Muang, Sakon Nakhon, THAILAND This study determines the requisite minimum initial capital for an insurance company to prevent bankruptcy, ensuring that the ruin probability does not exceed 0.01. We analyze discrete-time insurance surplus models across three categories: non-investment, bond investment, and stock investment. We examine the minimum initial capital necessary for non-investment, bond investment, and stock investment across various safety loadings. The ruin probabilities of three models are obtained through simulation, whereas the minimum initial capital is calculated using the linear least squares method. The results demonstrate that for safety loading levels ranging from 0.1 to 0.4, increasing by 0.1, the model's stock investment necessitates a reduced minimum initial capital in comparison to both non-investment and bond investment. For safety loading values ranging from 0.5 to 1.0, with increments of 0.1, the minimum initial capital for the three types is nearly identical. 03 27 2026 03 27 2026 166 13 https://creativecommons.org/licenses/by/4.0/deed.en_US 10.37394/23207.2026.23.13 https://wseas.com/journals/bae/2026/a265106-2223.pdf (text in Swedish) Lundberg, F. (1903). Approximate Representation of the Probability Function II. (Approximerad Fram ställning av Sannolikhetsfunktionen II). Återförsäkering av Kollektivrisker. Almqvist & Wiksell, Uppsala. Cramer, H. (1930). On the Mathematical Theory of Risk. Skandia Jubilee Volume. Gerber, H.U. (1988). Mathematical Fun with the Compound Binomial Process. ASTIN Bulletin, Vol. 18, 161-168. Tang, Q. and Tsitsiashvili, G. (2003), Precise estimates for the ruin probability in finite horizon in a discrete-time model with heavytailed insurance and financial risks, Stochastic, Processes and their Applications, Vol. 108, No. 2, 299-325. Chan, W. and Zhang, L. (2006). Direct Derivation of finite-time ruin probabilities in the discrete risk model with exponential or geometric claims. North American Actuarial Journal, Vol 10, 269-279. Sattayatham, P., Sangaroon, K., and Klongdee, W. (2013). Ruin probability-based initial capital of the discrete-time surplus process variance. Advancing the Science of Risk, Vol 7, 74-81. Nyrhinen, H. (2001). Finite and infinite time ruin probability in a stochastic economic environment. Stochastic Processes and their Applications, Vol 92(2), 265-285. Cai, J. and Dickson, D. (2004). Ruin Probability with a Markov chain interest model. Mathematics and Economics, Vol 35, 513-525. Azcue, P. and Muler, N. (2005). Optimal Reinsurance and dividend distribution policies in the Cramér-Lundberg model. Mathematical Finance, Vol. 15, 261-308. Boonta, S. and Kotsamran, K. (2023). Comparison of the minimum Initial capital of investment discrete-time surplus process in the case of separated claims. Wseas Transactions on Business and Economics, Vol 20, 1260-1267.