League of legends sites like LOLKing and LOLNexus makes use of the Riot’s official API (Riot Games API) for getting data about summoners, their match histories and statistics, and current game information. The important caveat is that the official Riot API only provides information for ‘‘Riot Regions’’, which is colloquial term for all the regions where Riot runs and maintains the game directly such as Brazil, Europe Nordic & NorthEast, Europe West, Korea, Latin America North & South, North America, Oceania, Russia, and Turkey.
There is no available information regarding an open API for the Garena servers. In Garena managed regions, implementation and use of API tools are at their discretion. Currently, they have elected not to make it available to the public and so there are no official tools available at this time. Some sources claim that there is an excessive price tag associated with getting access to that separate API.