The term 'เสียก่อน (sĭa gɔ̀ɔn)' is used in Thai language to denote the action that must happen before another action can take place, similar to the English 'first' or 'beforehand'. This phrase is typically used at the beginning of a sentence to introduce the primary action before shifting the focus to the subsequent action that follows. It can be used in various contexts to signify an action that precedes another.