Petrochemicals are chemical products derived from petroleum. Chemical compounds made from petroleum are also obtained from other fossil fuels such as coal or natural gas, or renewable sources such as corn or sugarcane. Petrochemicals are divided into two groups according to their chemical structure namely olefins and aromatics. Some of the olefins are propylene and ethylene while benzene and xylene are the aromatics. The petrochemical industry began in Thailand about fifty years. At that time the petrochemical industry was totally dependent on imports. But when natural gas reserves were found this really was a major boost up for the industry. Today the Thai petrochemical industry has tremendously grown and is considered to be the fifth best in the region. Thailand exports some of the major polymers to the foreign countries. Growths in other industries in have helped in the growth of the petrochemical industry.