I would suggest that this is subspecies layardi because it is the only one of the subspecies with the yellow undertail that is listed with current holdings on zootierliste, and the bird does look right for that subspecies generally.
I thought exactly the same. The only yellow-vented subspecies ZTL seems to list is P. b. layardi whereas other options could be subspecies such as P. b. tricolor. I'd say it's most likely P. b. layardi indeed.
