
1.
To run this must have wine preinstalled first
My Recommend tested: winehq-devel to run

2.
Run command this in terminal
winecfg

3.
Once enter winecfg configuration find & add sai.exe file 
& set emulate to Windows 98

4.
Now you can run Paint Tool Sai 1.2.5 on Linux

Note:
Wine can reset trial by delete .wine directory at your home/youruser/.
wine location with this you can run it clean. 
There is no piracy crack here but reset trial by your action.