Change League of Legends macOS language from Thai to English
By default the interface language will be locked to region, playing in TH server will result in Thai language and it cannot be changed within the game.
However it can be run from command line with
open /Applications/League\ of\ Legends.app/Contents/LoL/LeagueClient.app --args --locale=en_US
You may have to re-login, but the game will be in English.