Grateful thanks to Dave who sent these images following this post.
Check out the photos, especially the variation in flanks pattern with some showing the lines of thin pencil streaks, and others with more obvious cross bars on flank marks. Also the Slender-billed Curlew-like dark underside to outer primaries is apparent (barred dark/ pale in western Curlews). Nice white lower breast and belly, some have dark marks at tips of axilliaries and tail pattern– just visible in one or two shots.
I was out at Khok Kham (the nearest Spoon-billed Sandpiper site to Bangkok) yesterday afternoon and bumped into a flock of Curlew.
Having seen that you’ve recently raised some interest in the ID of orientalis on BF I banged off a few shots in case you wanted some additional reference material for birds in mid July. The best shots are attached here (sorry, nothing on the deck as these birds were a bit unapproachable). Those really are gleaming white underwings!