We run a company in Koh Samui and want to start business in Phuket.

Now we need to hire only one staff (foreigh national).

Can he or she work there legally with Work Permit issued in Samui or we need to open a branch or something like that?

Can we open a bank account there with the access of both General Director (based in Samui) and this manager?

Thank you in advance for your advice!

If the foreigner works in Phuket, this location must be in the Work Permit. This means yes, you have to register a branch office there.

Yes, you can open a bank account there with the signatures as you desire.