Koh Phangan 2012

[Psyche]

I have this as a very old and faded male C. bulis. However, I am now wondering whether this could be the female C. santana. (Taken with my old box brownie back in 2007)

Interesting, you have a male Curetis.
The forewing resembles C. bulis, but the hindwing does not.
The hindwing's orange cover almost the whole wing.
Below the left forewing the exposed part of space 7 is black (ended by the arching vein 7 arising from the radius (upperarm) of the cell & forming the upper border of space 6.)

I am fairly certain it is C. sperthis.
The upperside of C. sperthis is variable resembling bulis or santana, but space 7 is wholly blackened.(Correction: Key states only costa (upper margin) is black though whole of space 7 may be blackened.
The underside have black dots & the forewing band is less slanted to the termen.

TL Seow
PS. After looking at this for sometimes I think you are right. It is C. bulis male.
Even at its minimum the forewing orange patch of sperthis is like santana, ie larger & closer to the termen.
Wear had caused the black on the hindwing to fade to brown giving the impression that the hindwing is mostly orange.