To obtain a visa for Sri Lanka, you must:

• a passport with at least another six months of remaining validity after the date of entrance
• Show that you have the resources to support yourself during your stay.
• Evidence suggesting you'll depart Sri Lanka before the allotted time has passed (e.g. a return flight ticket).
• documents that attest to your trip's purpose A letter of invitation from a business, for instance, if you're going on business.
• The embassy you are applying in will inform you of the paperwork you need to provide if you are seeking for a resident, long-term visa for Sri Lanka.