Any game with a launcher, you usually need to Add it to Innerspace
http://isboxer.com/wiki/HOWTO:Add_a_Game, and then use the profile you have just created as the Game Profile for your characters when you go through the Quick Setup Wizard. In this case, your launcher is Garena Plus.
When you launch your character set via one of the 3 prescribed methods noted here,
http://isboxer.com/wiki/Quick_Start_Gui ... _3:_Log_in, the launcher should pop up. You log in to the game, you close the launcher, manually (maybe even End Task the process) if it doesn't have an option to close automatically (and no, minimized is not closed). When it is closed, Innerspace will launch the next one.
As long as you select POE from the Game drop down, it should do the necessary management to allow multiple instances, unless of course the POE Chinese version uses different mutex names to manage instance limits. Sounds like it might as the international version allows 2.
It is of course possible that even if you can close Garena Plus between launches that maybe it detects running games via executable names rather than by mutex, at which point it gets tricky because you can't just rename the executable of a running process. This is where you either need to do some digging to find out, or hope that someone else has the knowledge or time to find out.
Now, if you cannot close Garena Plus after each game launches because it will close down the game, you may not be able to do it.
You can check out mutex names by running Process Explorer by Sysinternals (now MS), selecting the game executable, pressing CTRL+H, and looking in the lower list for anything labelled Mutant.