Pseudophilautus fulvus — Knuckles Shrub Frog
My guide Udaya Chanaka identified this frog, and it was the only individual we found that he attributed to this species (or that looked like this). The pattern is quite distinctive but not a particularly good match for other photos I've found that are attributed to this species. However, it seems that no two individuals of this species have the same pattern, at least based on the few photos I've dug up. If you have a better idea please let me know!