You should own a legitimate license for Paint Tool SAI. Your license certificate can be downloaded from the official Systemax website and placed in the software folder.
Many users still seek "Paint Tool SAI 1 Portable" because it is smaller. However, for modern work: paint tool sai 2 portable
If you plug your Wacom/XP-Pen tablet into a public computer that has no tablet drivers, you lose pen pressure. SAI 2 Portable cannot install drivers for you. You must either carry a driver installer (requires admin rights) or use the mouse. You should own a legitimate license for Paint Tool SAI
SAI 2 is not a standalone new program but a rewrite of SAI 1, offering 64-bit support, higher resolution limits, and new brush engines. offering 64-bit support