Yes, a single member LLC can form an S Corp. This structure is popular among solo entrepreneurs who want to benefit from the tax advantages of an S Corporation and the liability protection of an LLC. Remember, while you're the only owner, your LLC is a separate legal entity from yourself for legal purposes.
Generally speaking though, the election to be a "S" Corporation, is at the Federal Level. At the Federal level, there is no requirement for employees, per se.
Disadvantage #1: Not Making Enough Taxable Income If your business is not earning enough income, the costs of an S-Corporation may outweigh the benefits. Many tax advisors believe that business income should exceed $40,000 before considering an S-Corporation.
In principle, an S corporation can have no employees.