can I plan my own business during employment

Before joining company have you signed documents any terms and conditions verify which may  impact you then after proced .

You can plan own business in parallel working at your work. You can try to open company register in singapore . On a web-site able to find all necessary and incremental information to begin own business. There is a list of necessary documents, and instruction from what to begin you.There is information as company regestration, to open a bank account, how to influence a record-keeping etc.