I read the book "les grandes chasses en Indochine" (big game hunting in Indochina)thanks to the link you provided me

In 1937 pricing in actual 2013 US dollars

safari one month 12 000 $

permit : 200 $
for
2 elephants
1 rhinoceros
6 bantengs
5 Gaurs (seladang)
4 water buffalos
the rest (tiger, leopard, croc, antelopes,deers are free and limitless)

incredbly cheap