#2
I can't think of anyway you can get there directly on VS miles, but there's a few options if you fly in-direct (e.g. via HKG, PVG). You can then grab a Thai flight from HKG (or maybe even one of the low cost carriers).
#3
There are a few options to get to BKK if you're willing to go indirect: via DEL/BOM with Jet Airways, BAH with GF, CPH with SAS or KUL with Malaysian.
Koh Samui is probably more tricky.
Edit: Malaysian codeshares with Bangkok Airways so you may be able to get to Koh Samui in one stop via KUL although I imagine you may not be allowed to redeem VS miles on a codeshare.
Koh Samui is probably more tricky.
Edit: Malaysian codeshares with Bangkok Airways so you may be able to get to Koh Samui in one stop via KUL although I imagine you may not be allowed to redeem VS miles on a codeshare.