What a terrible confusing mess.
You are right.
It should be Amblychia hymenaria.
In SE Asia including neigbouring Thailand, A. hymenaria have a distinct oblique white FW band.
https://www.mothsofborneo.com/part-1...miini_22_3.php
https://www.gbif.org/occurrence/1415534380
https://data.nhm.ac.uk/search
https://www.gbif.org/occurrence/2598681142
Strange to have banded form in S, India.(Correction : female have stronger band.)
https://www.gbif.org/occurrence/3988792638
Hampson's description.
https://archive.org/details/moths03h...p?view=theater
Matching images.
https://www.mothsofindia.org/sites/m...6ef6fe61-1.jpg
https://www.mothsofindia.org/sites/m...6ef6fe61-2.jpg
Amblychia nimia.
Prout's description.
https://archive.org/details/novitate...p?view=theater
Prout indicate Hampson's description of A. hymenaria should be A. procellosa, but 'procellosa' is now a junior synonym of hymenaria.
Correction: Prout was referring to Warren's description of hymenaria which should be procellosa.
Note UnF heavy with confluent spots.
https://www.mothsofindia.org/sites/m...549b2b28-2.jpg
https://www.mothsofindia.org/sites/m...549b2b28-1.jpg
Amblychia pardicellata
Walker's description
https://archive.org/details/listofsp...p?view=theater
Warren's
https://archive.org/details/moths03h...p?view=theater
More or less matching images.
https://www.mothsofindia.org/sites/m...fd44b281-2.jpg
https://www.mothsofindia.org/sites/m...fd44b281-1.jpg
https://www.mothsofindia.org/sites/m...63c10d6b-2.jpg
https://www.mothsofindia.org/sites/m...63c10d6b-1.jpg
TL Seow: Cheers.
PS.
Likely an intermediate cross, possibly with nimia.
The underside is as in hymenaria, but the white patch beyond the discal spot is rather weak
PS2.
All forms of A. hymenaria typically have some form of an oblique band on the FW.
From India & Sri Lanka.
https://www.gbif.org/occurrence/gall...n_key=11560614
Guenee's description of A. hymenaria is in French.
His description of the underside is as follow.
White underside, whipped with black, with a wide black border indented at the terminal edge by white spots that are missing between 1 and 1'.