The English version of Ragnarok Online Mobile version has been out for a while now that is a must try for the old school original RO players. The English version recently added the Thief character along with the Assassin class. Official game description below because mine is obviously boring.
Play Ragnarok anywhere you go! The legendary MMORPG goes mobile as Ragnarok Online: Valkyrie Uprising. Ragnarok Online has led MMORPG charge through the PC gaming world for over 10 years, and now it’s ready write a new history for the Mobile MMO world.
Join the adventure as you play with thousands of other players in real time to complete quests, missions, and battle against each other in the PVP Arenas.