The purpose of this thesis is to study the development and roles of commercial banks in Thailand from 1888-1945 during the period of the establishment of the first commercial bank in Thailand, the Hong Kong and Shanghai Banking Corp., in December 1888 to the issuance of the Commercial Bank Act of 1945, with special emphasis on their influences on commercial banks at present in form of pattern, structure, management and contribution to the country’s economy as a whole. The studies found that the commercial banking in Thailand was firstly established to offer financial services to the trade business which had developed rapidly since Thailand signed the Bowring Treaty type in 1850’s Thai commercial bands were influenced by the British Commonwealth’s Banking pattern and system: the branch banking management was arranged to support foreign business and trade. Besides the Compradore system was also put into practice. The management of commercial banks depended upon banker’s policies which had to comply with obligations under the laws, rules and regulations laid by the Government in order to control the banking operation. The Government supported commercial banks since the beginning. But, at the same time, the law, cevil agents and officers supervising the banks were not efficient enough. Therefore, improvement and amendment were introduced to eliminate all the loopholes in trial and error manner. Concerning banking control, the study found that Government’s primary concern was not only to protect public interest but also to supervise the banking operation to the advantage of social economy. Most of the bankers were both Thai and Chinese who accumulated wealth through internal and external trade. Consequently, they were people who ran different kinds of business at the same time. Trend of advances was then to finance their concerned business Moreover, all the bankers had inter-relationship either by business, ralatives and societies which were united by common interest. Thai commercial banks were therefore the monopoly of some influencial groups who held the business and trade net work within the country. During the period, commercial banks developed gradually and steadily which could be seen from the number of branches, deposits and advances increased every year. However, comparing with the number of population, the amount of deposits as well as the amount of advances was still not high enough and centralized in Bangkok and provinces with economic potentials only. In accordance with county’s money economy, the commercial banks played the roles in issuing bank notes, sharing foreign exchange activities and creating credit money. For economic development, they were the only important private financial institute for financing foreign trade especially the rice export. Moreover, the roles of British and French commercial banks in Thailand in supporting the Government’s loans in London Capital Market during 1901-1904 indirectly affected the country’s economic development for the loans were used in railway construction and irrigation.