I heard my name mentioned here. thank you, joseff.
this "thing" is difficult yet fun to ride. here in Indonesia, we have a variety of becak designs. for example, becak from Jogja, like yours, is different from the ones from Malang or Surabaya, for example. becaks from East Java are tend to have long wheelbase. I never comprehend why.
from the fender design, I'd say yours is from Central Java, from Semarang or Surakarta maybe.
in some regions of Sumatra, the rider (or driver, if you prefer that) sits on the right side of the vehicle, so it's more like a sidecar.
becaks are not legal in Jakarta, unfortunately. but again, if you want to trade becaks with track bike frames, we'll be gladly not to refuse.