PTT invests in the oil refining and integrated petrochemical business through companies in the PTT group. The PTT group operates oil refineries with modern and highly efficient production processes, with a total refining capacity of 770,000 barrels per day. PTT is involved in sourcing crude oil and purchasing finished oil products from oil refineries in the PTT group in quantities at least proportional to PTT's shareholding for resale to customers.

Additionally, PTT has invested in the integrated petrochemical business through companies in the PTT group, starting from the production and sale of basic, intermediate, and final petrochemical products, including both olefins and aromatics, focusing on creating added value for the business through the development of specialty products and creating business opportunities based on market demand (market back strategy), as well as providing storage and distribution services for petroleum and petrochemical products. Currently, the PTT group is one of the largest producers of petrochemical products in the country and a leading producer in the Asia and Southeast Asia region.