Holding current of a thyristor
The anode-to-cathode voltage at the holding current is usually around a volt. Of course the holding current is much less than the maximum forward current. Take a typical smallish thristor, the S6025NRP 25A/600V SCR. Holding current is maximum 50mA. Perhaps not surprisingly, it's similar to the gate trigger current of 35mA maximum. 

From the datasheet you can see the variation in holding current vs. temperature, and the on-state voltage, which will be about 0.85V typically at ~50mA. 



Of course it's up to your circuit (such as the load) to limit the forward current. The SCR just acts as a switch.