Changing planes in BKK need advice
 

I'm flying into BKK with Qatar airways 832 hoping to catch Jetstar 30 to Melbourne. The layover is about 3 hours. I was wondering if there is an interline agreement between these two carriers or if I will have to clear immigration and go through that process.

How can I find out if an interline agreement exists between these two carriers.

Looks like they might have an interline agreement with QR.

The link above given by BuildingMyBento specifies Jetstar Asia (3K).
Here is the link with same information but referring to the whole Jetstar Group. I'm assuming you are flying JQ. I suggest you print out this page and have it handy in case Qatar gives you problems at the airport.

Looks like they mention QR anyway.

Anyway, even if no interline agreement, there is plenty of time with a 3 hours layover to clear immigration. exit customs, proceed to departures level (1 floor up) and check-in with Jetstar landside.

Thanks BuildingMyBento,Gilbert are, and SK AAR for all your great help.