Can you recommend a rough pack-list?

Try getting a sarong. It’s very light, comfortable and packs down to almost nothing; also it suits all purposes and occasions, including the temple etiquette.

What type of clothes should I pack?

Lightweight, light coloured cotton clothes are ideal for the warm climes of a tropical country like Sri Lanka. We’d like to recommend that you pack some warm clothes if you are planning to visit the hilly regions, where the evenings tend to get chilly.