You are welcome with your UAV in Sri Lanka
Maximum take-off weight: Above 250 gram you have to following UAV rules
Maximum hight: 120 meters 393 ft.
Maximum horizontal distance: In build-up areas 450 meters / 1,476 ft. outside: 750 meters / 2,460.
Insurance: Liability insurance obligated
Distance Airports/Heliports: 5 km 3.18 miles
Distance Borders: Not within 50 km / 31 miles from Borders
Fireproof tag: Obligated, with Name, Adres, telephone number. Order it here.
Maximum UAVs: A Pilot may only fly one UAV at a time
Sea Distance: Not further then 500 meters / 1,640 ft from Coastline
Minimum age: 18 years
Night fligts: Obligated
Prohibited: not above humans, animals, buildings, beaches, buildings military objects, government buildings.
Special attention: - Not within 5 km from Airports
- Do not fly in Wild or National parks, or above a Zoo
- Use a UAV only when it can register a flight log.
- UAV must have a GPS and Return to home
- UAV must have lights.
Useful Link: Ministry of Civil Aviation