This is a spell checker for Sinhala - compatible with all major platforms.
To use, just install the extension and select Sinhala as the language from "Tools > Language > For Paragraph > CTL Font (Language field)". If you don't see CTL font section, you may need to enable it from "Tools > Options > Language Settings > Languages > Enabled For Complex Text Layout (CTL)".
Send your comments/suggestions to blaknath [at] gmail [dot] com
3.0.2