You are quite right.
There are three of those obscure Thoressa species in the area which are quite similar.
Thoressa aina.
UpF spots are distinctly yellow, the cellspot prominent.
https://archive.org/details/journalo...p?view=theater
Fig 8.
https://archive.org/details/journalo...p?view=theater
Thoressa fusca.
Twin cellspots may be absent.
Male brand very obscure.
http://yutaka.it-n.jp/hes/91245001.html
Thoressa gupta.
Twin cellspot may be absent.
Male brand prominent with two spots.
UnH plain or vaguely spotted.
Fig 1.
https://archive.org/details/journalo...p?view=theater
From China.
Colour plate III Page 164- 165.
Fig 4 - 7 T. gupta.
Fig 8- 9 T. fusca.
https://www.zobodat.at/pdf/Neue-Ento..._0003-0114.pdf
TL Seow: Cheers.