That’s plenty of time for an int-domestic transfer at BKK. I have no experience with visa on arrival but even if it takes 30mins you will still have loads of time. You already have fast-track from your inbound J ticket so no benefit in purchasing that. You can book a buggy service to pick you up at the gate and drive you to immigration but it will only save max 10-15 mins really.

On arrival just follow the signs to domestic transit then (if you haven’t checked in online) can collect PG BP at the transfer desk. Straight through immigration and security and to the PG lounge. I would say on average it takes me about 30 mins from landing to being in the domestic departures lounge (but I don’t need a visa).