I need a copy of a book called 'Chang Pook' - about a person called
SEBAT and an elephant called NAMBA - based in Siam ...

Hello there

I think you mean "Chang Phouk" by Smith, Jane Davis, and Holaday,
Diane
(Illustrator) 
Trade Paperback. 1stBooks Library (04/2001), ISBN: 0759611742 


I've found two copies available

There is a new copy at Alibris for $10.76
Alibris have it in stock and they can ship in one day

http://www.alibris.com/search/search.cfm?nwork=1009933&ptit=Chang%20Phoouk&pauth=Smith%2C%20Jane%20Davis%2C%20and%20Holaday%2C%20Diane%20%28Illustrator%29&pisbn=0759611742&pbest=19%2E95&pbestnew=10%2E76&pqty=1&pqtynew=1&qsort=p


There is a used copy at Alibris for $19.95, advertised as like new,
sourced from a bookstore through Alibris

http://www.alibris.com/search/search.cfm?qwork=1009933&ptit=Chang%20Phoouk&pauth=Smith%2C%20Jane%20Davis%2C%20and%20Holaday%2C%20Diane%20%28Illustrator%29&pisbn=0759611742&pbest=19%2E95&pbestnew=10%2E76&pqty=1&pqtynew=1&matches=1&qsort=p

Hope you get what you want

Willie