Singapore EP's minimum salary requirement ranges from $5.6k per month for age 23 to $10.7k per month for 45 years old. For the newly start up company, the share capital should cover at least 1 year salary in general. That's is where the $100k share capital estimate comes from.
For an operating company, if the company has revenues sufficient to pay for the annual salary, that will be taken into account and need not top up the capital.
If the company doesn't have revenue nor share capital, his contracts and sales agreement from his overseas' entities and companies work as well (as a supporting document︀ that the company indeed has the funds to pay for his salary).
There are no︁ officially guidelines but are figured out by the market based on the results of the︂ rejections and passing cases, all from personal experience.