The amount of retrenchment benefit depends on what is provided for in the employment contract or collective agreement (for unionised companies). If there is no provision, it will have to be negotiated between the employees (or their union) and the employer.

你的雇佣合同里有写裁员的赔偿吗？我做了这么多年工，反正除了代通知金，从来没读到过其它保障。
https://www.mom.gov.sg/employment-practices/retrenchment/responsible-retrenchment