ajohn

I agree with bin_go that this appears to be an Eastern Curlew. Eurasian should normally show a pure white, unmarked underwing, as shown in the second photo.
It is unusual, however, for the underwing to be so pale on an Eastern Curlew, and for the rear of the underparts to be so pale.
Are there any more photos showing the upperparts of the bird to confirm whether the rump was white or dark? Looking closely at the photo, it looks like the feathers of the rump are barred (which would support the ID as Eastern).

ajohn

I decided to take a new look at this photo after watching Far Eastern Curlew at Mai Po this spring. I agree with Ho-fai that the overall colour of the bird fits better for Eurasian rather than Far Eastern.
The barred underwing does not fit with typical orientalis Eurasian, which is the subspecies found in HK. I don't know about the variation in orientalis, but as Ho-fai suggests this may be from the western subspecies arquata. This would be the first HK record of this subspecies, which breeds west of the Urals and winters in Africa, and is therefore a surprising vagrant. As Ho-fai suggests, I recommend that you submit the record to the records committee for assessment.