Self employed in Germany (Singapore)

Hallo everybody!

Maybe you can help me with this question:
My husband might be sent with his company to Singapore. I'm working as a self employed grafic designer here in Germany. I have several clients I would love to continue working for. With computer and Internet no problem. Of course I used to do my tax declaration here in Germany. I always include the German tax in my bills. Would this have change because of my move to Singapore? Do I have to get a work permit for me? Open up a business?

Thanks for your replies in advance!

Karin