Recently flew these legs booked in Y+ on very decently priced sale fares - was initially on a non-refurbed 3-class 744 both ways, and had been allocated Y+ -> J cabin (rows 23-24) due to SG - and maybe they don't use that cabin for J any more to avoid putting J pax in a position where they can end up in the middle of three seats?
The outbound aircraft was subbed a few weeks out to a refurbed 744, so we did a points upgrade to J (first time in the Mk II refurb seats, very 380-like in the upper deck, so very happy). Inbound there was no aircraft change (so Mk I seats) however it appeared that most of the 'Y+' cabin were points/op-uped to J at T-24hrs (except us, naturally), yet the cabin was still full on departure - so a few lucky Y pax got the double upgrade to Y+ in a J seat (either using points on op-ups - I'd say at least a couple of op-ups from those I spoke with). Can't complain though, as it worked out nicely for us in general - a slightly better meal in the same seat wouldn't have been worth the points spent on upgrading to J.
Enjoyed the flight, onboard service was great both ways in 'both' cabins - ground service ex-MEL T1 was pretty poor though, despite the same day J departure and SG was directed away from the premium check in desk until I insisted, bags were not given J tags (or even priority) and was not properly informed of the SYD transfer procedure (which I knew, but still thought was from gate 2 so it was lucky I double-checked on board). Disappointing to have to connect in SYD as well, the transfer is a right pain given you have to wait a couple of bus-loads to get a seat and still have to clear security again (train would be simpler, despite the $5) - and SYD was so packed on the day that the line for the TRS refund snaked through half the duty free area, so I just gave it up (but that's another matter).
As for Bangkok, it wasn't too bad while we were there - though the 'shutdown' has commenced now, so I imagine traffic will be awful. As per TravelingSmithy and thanks to a referral on another thread, following @RichardBarrow was an invaluable source of information as to what was going on where in and around Bangkok. Still seems like there's plenty of people coming in and out of Thailand despite the turmoil, which so far hasn't been quite as bad as 2010 or earlier.