Hello there, RIOT is going to implement Garena regions to its API, so I will implement them to the app when it is available. Check the RIOT post from its forum below of this lines. Greetings!
We are really happy to announce that the Riot API is coming to the Garena region! The Beta version of the API will include the champion-mastery, champion, league, summoner, and third-party-code endpoints with match history and spectator coming later. Our team is already working with OP.GG and Garena in order to test the deployment of these endpoints. OP.GG will be releasing a version of their tools for the region shortly, so check with OP.GG for more details at www.op.gg/garena/. Once we feel we have gathered enough data from this Beta test, it will be opened up to all developers.