Where to find mapping of Air Canada G-class fare onto ThaiAir

Does anyone know what a G-fare ticket on an Air Canada codeshare (operated by ThaiAirways) maps to on Thai Airways? (Or how to find out)

I am trying to put in a retro-claim for a flight, and the submission box asks for the fare class. The system wants the ThaiAirways flight details (rather than the codeshare number) and unfortunately the booking code. G-Class on Thai earns nothing, whereas on Air Canada it was a flexi fare and I’d expect it to earn something.

*I know to avoid codeshares where possible, unfortunately it was the op my option for the fare and routing*