Any way to check award availability on PG before the transfer? It would be pretty dumb to transfer a decent chunk of SPG and have it get stranded in an orphan account if there wasn't award availability...

OP: In theory you can connect in PEN instead of BKK and fly FY to USM; CX 633 arrives about 2 hours before FY 3602 leaves. The catch is... separate tickets. The tickets are generally more reasonable than PG's, especially around peak travel times to Ko Samui (like December, Full Moon Party, etc.).

I don't know if buying an FY ticket as the MH codeshare through MH would get you under the oneworld guarantee of IROPS protection on separate tickets (sadly, you can't book FY through oneworld awards). Depends on what your tolerance for risk is (that or do an overnight stay in PEN to minimize risk, like I did- Georgetown is certainly not Bangkok but it has it's own charms).

The cheapest LCC options involve some airline like DD and connecting through URT, plus a bus and ferry ride, as Unterwegs mentions. Not bad but chews up a lot of time.

I would be disinclined to burn many miles on a couple hundred dollars of airfare in SE Asia, especially when the LCC options for flights are perfectly reasonable.