Polygala venenosa

This is a giant and more horticultural interesting member of this large cosmopolitan genus with a common name of milkwort. In Malaysia, members of this genus are mostly inconspicuous small ground herbs  ....

but this species is up about 2 metre tall and bears many pendant inflorescence with few flowers opening only at the tip. As the flower drops, the bract elongate and show signs of scars where the pedicels were attached. The flowers, each about 2 cm long, change hue from white, yellow to purple as they mature. 

As you can see, the inflorescence can be quite long, up to 30cm although usually shorter.

It is supposedly a montane plant but I found this population in Pahang lowland. Its distribution extend north to Thailand and south to Borneo and Java. Many Polygala species are used in folk medicine but as its latin name suggests, this species is said to be toxic, and can cause nausea and giddiness just by touching (as per Philibert Commerçon,  a renown medical doctor / botanist in 1700s and the collector of the type specimen in Java). More recently however, M.R. Henderson mentioned in "Malayan Wild Flowers" that local population was not known to be poisonous, and having handled the plants myself, I can attest to that.