There is space on the 25th in C SFO-ICN-BKK. First flight is on OZ the next two are on TG.

The return isn't showing anything into SFO in C. There is UA F there if you have the miles and want to use them. I'm trying to find any flight in C to the US on your dates and can only find F. There is a flight into JFK on EgyptAir which is a poor redemption value and a connection in CAI is required.

Another potential solution would purchasing a revenue ticket to Mumbai where there are several connections open. SQ has C space through SIN to ICN linking up with the UA flight to SFO. This flight leaves BOM at 22:10 so connecting isn't an issue.