I found some older discussion of these two species on Butterfly Circle, but it did not seems to come to any conclusions on good features to separate these two confusing species. I attach a number of images, of which the three from Nan and Phrae provinces I have tentatively identified as aliris but would be interested in some feedback on how to separate these.

Image 1, from se Thailand, should be T. laythi, due to predominantly reddish tinge, and aliris being unrecorded from se Thailand.

Image 2. Is assumed T. laythi from Doi Suthep.

Image 3, 4 and 5 are assumed T. aliris, based purely on them not being very bright, but does wear affect this? Interested in feedback on any morphological differences. Many thanks

Image 1. T. layhti from Khao Soi Dao
b2165 Siam Jungleking (Thauria lathyi siamensis) - Khao Soi Dao 02.JPG

Image 2. Assumed T. laythi from Doi Suthep.
b2160 Siam Jungleking (Thauria lathyi gabrieli) - Doi Suthep-Pui 01.JPG

Image 3. Assumed T. aliris from Phu Soi Dao (Nan province)
b2170 Tufted Jungleking (Thauria aliris intermedia) - Wiang Kosai 01.JPG

Image 4. Assumed T. aliris from Wiang Kosai (Phrae province)
b2170 Tufted Jungleking (Thauria aliris intermedia) - Phu Suan Sai 01.JPG

Image 5. Assumed T. aliris from Tham Sakoen (Nan province).
IMG_1987.JPG