Thai Prime Minister Yingluck Shinawatra and visiting South Korean President Lee Myung-bak reached the agreement during bilateral talks in Bangkok.
Mr Lee, who arrived in Bangkok on Friday, is the first South Korean president to make an official bilateral visit to Thailand in 31 years.
According to the joint statement after the talks, the leaders also agreed to "serious efforts" to conclude a trade and economic cooperation "action plan" for 2013-2017 at an early date to further energise trade and minimise trade barriers. They asked the joint trade committee of both sides to start negotiations as soon as possible.
Trade between South Korea and Thailand reached an all-time high of $13.9 billion last year.
Bangkok and Seoul have agreed to seek preliminary discussions and a joint study about forging a comprehensive economic partnership agreement in order to strengthen economic links between the two countries, said the joint statement.
Ms Yingluck and Mr Lee have welcomed cooperation in various Thai infrastructure projects, especially its water management system, high-speed train line, power plant development projects and the Dawei deep sea port project.
During her visit to South Korea in March, Ms Yingluck expressed keen interest in South Korea's project to revive its four major rivers in a way that prevents floods, preserves water resources and promotes tourism along the waterways.
South Korea has expressed interest in importing rice from Thailand in response to higher demand while many Thais fruits including mango, longan and pomelo are also favourite choices for South Koreans.
Both leaders also called for launching aviation talks at an early date to facilitate people-to-people exchanges and transfers of goods and services at a time when the number of people visiting each other's nation topped 1.3 million last year.
After the meeting at Government House, Mr Lee toured the Chao Praya River and the Lad Pho canal, a move seen as underlining South Korea's willingness to share its water management experience and know-how. Thailand is working on a massive $11.3 billion project to build a large-scale water management system.
Mr Lee is scheduled to return home on Sunday.