which company is that? did you sign contract?
does the contract mention the 400 SGD and promise to return the money to you?

面试了吗，签约了吗，什么行业的
如果是上岗培训，如果怕员工跳槽或泄密完全可以合约来绑，交钱培训闻所未闻。。。。400元的机密。。。

一个物业管理公司

they promised to give us the receipt once we handed S$400. They claimed the money is for candidates to attend the course everyday(5-day course), if you miss one lesson, the 400 deposit will not be returned. They said the company paid for the course and lecturer, so all the candidates must make sure to attend it every day. After the course there is a test, if you pass the test you'll be offered the job. Do this credible?

没有签约，还没拿到offer

只是参加培训，公司需要我们每天都听课，缺课的话也扣押金。

be careful ! it is probably a trap! google the company and
any related infor to find out more.