Dr. Thirachaya Chaigasem, Amarawadee Kumboon. “Frontier Tourism in the Pattern of Twin Cities Located in Thailand and Lao People’s Democratic Republic on Structural Model ”. PalArch’s Journal of Archaeology of Egypt / Egyptology, vol. 17, no. 9, Nov. 2020, pp. 5416 -33, https://www.archives.palarch.nl/index.php/jae/article/view/5012.