I connected a few month ago from CX to Bangkok Airways (domestic). It seems similar to the procedure on Thai i did two/three years ago.
But it is not as easy as it seems....

TG and Thai have connection counters on the arrival floor. We had no problem getting the boarding pass for the domestic flights there (and the sticker). In front of us was an australian couple which came in on QF from SYD. They wanted to go onto the same flight and where told they need to clear immigration and then walk over to the domestic terminal. We (US and german passports) could juist go directly to the gate.

There are two gates for the same flight, one in the domestic terminal and one in the international. Two busses to the same plane.

On arrival there are multiple busses again and people with passenger lists who make sure that the domestic passengers and the international are seperated again. One goes to domestic arrival, the other to international....

Similar on the way back: two gates for the same flight to BKK, one for international connections and one for BKK. One group goes thru immigration, the other does not. Both end up on the same plane. On arrival the same seperation procedure, one bus to the International Terminal, one to the domestic.

Time: Total walking time if you can stay inside the international terminal is 5-15 min to the transfer desk and then 5 min to the bus gate. So 1 hour is plenty of time.

If you need to go landside it can be a fairly lengthy walk to the domestic terminal, my guess is that you would be lucky to do everything in less than 1 hour.