Euploea eyndhovii or Euploea doubledayi

[Psyche]

it is impossible to be certain based on the underside alone.
The two were basically the continental & Sundanian representatives of a single species.
When Malaya (part of Sundaland) joined the mainland E. eyndhovii moves north into peninsular Thailand & E. doubledayi south into the northern half of Malaya.
As Yala is part of Sundaland it is probable E. eyndhovii is the commoner there.

E. doubledayi : Larger FW darker ,often blue black, Female always with a few central spots .
Umderside HW stripes usually broader, HW central spots many if stripes large ; few if stripes smaller & shorter.
http://wingscales.com/content/record/2508-1-9bc82.jpg
http://www.ifoundbutterflies.org/med...gale_ah162.jpg
http://www.samuibutterflies.com/02_i...doubledayi.jpg
http://malaysiabutterflies.myspecies...s/IMG_0483.JPG

E. eyndhovii; smaller ofteb rather so, FW male blackish brown, female upperside FW unspotted. HW central spots usually many ,variable.
Singapore have only E eyndhovii.
http://butterflycircle.blogspot.my/2...mber-2016.html

This looks like it should be E. eyndhovii.

TL Seow: Cheers.

[DaveChiangMai]

Thanks. E. eyndhovii was my feeling based on the width of the underside stripes, but as you say variable when looking at images across the web.