Muangmor, Hanusit, Panupong Upala, and Tawatchai Apidechkul. 2020. “COVID-19 Outbreak in the Chiang Rai Border Area Due to Illegal Immigration to Thailand: A Field Investigation”. Journal of Health Science and Alternative Medicine 2 (3). Bangkok, Thailand:22-28. https://he01.tci-thaijo.org/index.php/jhealthscialternmed/article/view/246326.