LifeinAsia - 5:25 pm on Jun 12, 2013 (gmt 0)
Like all things legal, "It depends."
Do you have an employment agreement (signed by every employee) that fully and specifically provides that the employer owns IP created by an employee in the course of the employee's work duties? This is known as an "assignment-of-inventions" agreement and should be signed BEFORE the employee starts working.
Having them sign something now *may* protect you going forward, although an employee could always try to show that he/she started development before signing the agreement, so doesn't apply.
As always, IANAL, so take with a grain of salt and always seek legal advice from a licensed and experience practitioner. :)