It seems that apart from the citizens of Maldives, Seychelles, and Singapore, nationals of all other countries are required to obtain a visa to enter Sri Lanka. To attend the conference, you can apply online for a TOURIST Sri Lankan visa by clicking the ETA link given below and following the instructions given on the ETA website. In filling out the ETA form, select the “MICE (Meetings, Incentives, Conferences, & Exhibitions/events” option to indicate the purpose of your visit.
For further information about the Sri Lankan visa, the conference participants are referred to the following website: