Potanthus confucius dushta.
http://yutaka.it-n.jp/hes/92790010.html
P. confucius have been photographed in the past but some shots are less than ideal & most are labelled as P. omaha.
Generally yellower overall.
Abdominal end yellow with at most a thin basal black ring.
FW with spots 4 & 5 broadly overlapping the spots above & below them. (Less in the female.)
Bands with the veins not dark-dusted (or just lightly), edged with diffuse dark spots & ground lightly dusted.
Male FW upperside with the band continuous uninterrupted by dark veins.
Female veins may be lightly dark, FW lower three spots broad.
These Thai males are very fine.
https://wingscales.com/Hesperiidae/P...nfucius-dushta
Male by Federick probably 12 years ago. Note FW with the spots broadly overlapping.
https://3.bp.blogspot.com/-B2W0fVicL...-confucius.jpg
More recent shots .Males.
2018.
https://www.inaturalist.org/observations/12289699
https://www.inaturalist.org/observations/163651656
The distinctive continuous yellow band in the male.
https://www.inaturalist.org/observations/172635778
https://www.inaturalist.org/observations/103448632
Veins slightly dark -male.
https://www.inaturalist.org/observations/145880950
Compare the upperside of a male P. omaha with distinct dark veins below.
https://www.inaturalist.org/observations/172978891
And a male P. ganda .
https://www.inaturalist.org/observations/162823627
The Taiwan subspecies angustatus ( "narrowed ")
Have slightly narrower bands & the abdominal end is darker.
The female is quite similar & can be used as a reference for local females.
http://digimuse.nmns.edu.tw/butterfl...7%CB%BD%BA.xml
Addendum :Females. Note large HW spot 6.
https://www.inaturalist.org/observations/86144160
https://www.inaturalist.org/observations/102403053
Federick's shot ?12+ years ago. Note FW spots overlapping, veins lightly dark, HW spot 6 large, & ground heavier shading.
http://2.bp.blogspot.com/-nfGuHY9hc3...28TBC%2529.jpg
Female. Distinct yellow; FW spots with wide overlaps; HW with large spot 6.Veins weakly dark.
https://www.inaturalist.org/observations/173920049
Females P. omaha for comparison.
https://www.inaturalist.org/observations/106791445
https://www.inaturalist.org/observations/103303782
https://www.inaturalist.org/observations/147267181
https://www.inaturalist.org/observations/162137058
https://www.inaturalist.org/observations/162440420
Female P. ganda.
https://www.inaturalist.org/observations/90387121
TL Seow: Cheers.
PS. Not rare. There are a fair number of observations.