Applicants can find process of test fee refund of each test center that you registered at below links;
Bangkok Test Center
Website: https://www.ojsat.or.th/main/jlptrefund-1-2020-bangkok/
Facebook: https://web.facebook.com/OJSAT/posts/3103275526363449
Chiang Mai Test Center
Website: https://bit.ly/2VzqoUa
Facebook: https://web.facebook.com/ojsatn/posts/2889559734467481