TBH, it’s not optimal, and you should pursue compensation,, but JQ 787 service isn’t quite as bad as many make out the worst feature of these services is punctuality. However if they won’t make alternative arrangements (such as putting you on TG or on QF 35 to SIN connecting to TG to BKK, which they are selling on their website) I would expect that QF should at the very minimum reimburse you for IFE and meals and beverages on the JQ flight. And of course Original Routing Credit (unless it is higher on the JQ flight; which it may be depending on fare class).
