Sri Lanka has only one coal power plant (construction began 2006), and the later coal project was canceled.

https://en.wikipedia.org/wiki/List_of_power_stations_in_Sri_...

You are correct its only one but its gone from zero in 2010 to about half of what hydro produces now, and the proportion from renewables has gone down quite considerably: https://en.wikipedia.org/wiki/Electricity_sector_in_Sri_Lank...