May be useful for political stability, but I don´t know whether there is data for Sri Lanka.

https://sites.google.com/site/pippanorris3/research/data

I suggest: 

https://www.cia.gov/library/publications/the-world-factbook/

Also: 

https://freedomhouse.org/report-types/freedom-world

http://www.transparency.org/cpi2015?gclid=CjwKEAiA__C1BRDqyJOQ8_Tq230SJABWBSxnn__7Ha1c_JOQ0Jld8csACdczf9itpp91l-IypI7_MRoCCVPw_wcB

Transparency.org would be your best bet in terms of political/institutional corruption.

Regards.

You can check Polity index.

I suggest the Worldwide Governance Indicators (WGI) project:

http://info.worldbank.org/governance/wgi/index.aspx#home

Other than those mentioned above, you might want to check http://www.democracybarometer.org/links_en.html. They have compiled links to various governance/institutions/conflicts datasets.

Thank you very much for your suggestions

I found this link  www.theglobaleconomy.com/rankings/wb_political_stability/; Country rankings using data from official sources.