The Siamese lived for centuries of off rice growers in the countryside. For profit they sold various valuables, for example, lacquer, rare woods, and elephants. This sort of living style still exists in modern day Thailand, which displays it's effectiveness.

During the Sukhothai period (first Siam kingdom) the Thai grew rice for their own consumption and to pay taxes, and whatever remained was used to support religious institutions. However as the Ayutthaya kingdom emerged, Sukhothai soon diminished. It is during this period (13th and 14th centuries) that a drastic change took place in the Siam economy._39908127_china203ap.jpg

Soon after (1500's) the Portuguese came to Ayutthaya having been attracted by their large markets. After came the French, Dutch, Ayutthaya was located at the confluence of 3 rivers (the Lopburi, Pasak, and Chao Phraya) which made it a remarkable trade center. Rice, for example, and East India companies. Upon the arrival of these foreigners the Siam's trade began to grow. With the growth of foreign trade Bangkok became an important spot where goods were transported to Ayutthaya. Ships dropped off cargo at Bangkok, and from there smaller ships sailed up the Chao Phraya River to deliver the goods.

Some of the materials Ayutthaya possessed were gold, silver, lacquer, porcelain (ceramic material), Persian and Indian
carpets, and other various objects that came from Japan and China.

Sources:
PEM. 10 Oct. 2006 <http://www.pem.org/press/index.php?id=50>.

Thailand - Economic Development. 10 Oct. 2006 <http://countrystudies.us/
thailand/10.htm>.

Spitzer, H.M. "Far Eastern Survey, Vol. 15, No. 9 (May 8, 1946), pp. 139-141."
JSTOR. 8 Oct. 2006 <http://links.jstor.org/
sici?sici=0362-8949%2819460508%2915%3A9%3C139%3ASEP%3E2.0.CO%3B2-E&size=LARGE

Picture
BBC News. 8 Oct. 2006 <http://news.bbc.co.uk/2/hi/science/nature/
4495775.stm>.