Enforcement rules concerning the implementation of industrial group act. Article 23

The vacancy or absence of directors and supervisors are to be filled by backup directors and supervisors within one month. When no backup directors and supervisors are available and the number of directors and supervisors exceed two thirds of the stipulated number in articles, no by-election is necessary.
中文原文 工業團體法施行細則第23條
工業同業公會理事監事出缺,應於一個月內由候補理事候補監事依次遞補。
無候補理事候補監事遞補而理事或監事人數超過公會章程規定全體理事或監事名額三分之二以上者,不予補選。

English translation for reference only; the Chinese text prevails. Not legal advice.