Palanandana, K., and D. Kraipakorn. “Simo Wichai’s Worldview: The Study of Simo’s Letters during 1889-1890”. Journal of Thai Studies, vol. 15, no. 1, Mar. 2023, pp. 1-32, https://so04.tci-thaijo.org/index.php/TSDJ/article/view/264059.