Yes, you can apply for more than one master’s course at ISI Kolkata but you won’t be able to appear for more than one entrance examination. 

• All the entrance exams are conducted on the same day at the same time, therefore you will not be able to appear for more than one examination.
• Technically you can fill the application forms for more than one examination if you are a bit confused at present and want to have safe options. You can apply using two different email IDs to register and make the payments for both of them.

But in the end, you will have to decide which exam you want to prepare for and appear in.