Nepenthes bokorensis is a species which has been overlooked several times. It was recently recognized and named by Francois Sockhom Mey in 2009. Previously, it has been incorrectly identified as N. smilesii, N. thorelii, and possibly as N. kampotiana. It has also been used to make horticultural hybrids at least as far back as the 1970's in the USA.
Unfortunately, most of these plants (both N. bokorensis and N. smilesii) eventual went dormant in cultivation. Thinking their plant had, people threw them out, not realizing this species can go dormant during winter or when the weather turns dry. A couple of lucky folks were able to save their plants because they had tossed the soil from the pots onto the compost heap, only to find the plants had started re-growing several weeks later.
I received my female plant under the name Nepenthes thorelii in 2006. When I inquired about the location information, it was explained this plant is believed to have been collected from somewhere in Indochina, the exact location unknown. Because I reviewed photos of the type specimen, I realized the plant was not N. thorelii and called it, "Dave's unknown Nepenthes species A".
This photo is a virtual herbarium from 2007, five links can be found. Click on the different parts of the plant to see close-up photographs.
There are several species from the area, and they have all been called "N. thorelii" at one time or another. One discrepancy I noticed, this seems to be a highland plant and N. thorelii is supposed to be a lowlander... It also seems rather similar to this more gracile unidentified highland species from Langkawi Island in Malaysia as the lower pitchers appear close, but the lids and peristomes are different. Unfortunately, my plant still only makes lower pitchers; but it recently flowered, so maybe upper pitchers will grow soon.
Here is a photo taken by a tourist Don Pirot in Phnom Bokor National Park, near the Vietnam border. There is also the tuberous Drosera peltata, growing right next to the similarly tuberous Nepenthes. This species appears most closely related to N. smilesii.
Please checkout Nepenthes of Thailand for information about this species.