Sadhukarn is one of the most important song. having been using in the Thai musical ensemble for several centuries. The song is quite important to the Thai musical culture since it is performed as the first song of most musical ceremonies. The song is used for paying homage and respect to Lord Buddha, and is also used for the biginners of the Thai traditional music classes. Unfortunately, the composer of this song is still unknown and yet the musicological analysis of this song has never been completed. The Gong Wong Yai (large horizontal round Gongs set) is used in this research to play the basic melody of the song Sadhukarn the melody were recorded from ten selected outstanding and along time experienced Thai music teachers from several Thai musical institutes. The anlysis is completed in several aspects such as : the basic melody form, sentences, phrases, rhythms, technique of hands performing and the special characteristic of the "note ending" seen in each sentence and phrase of which these ending notes were called the "Look-Tok". Results showed that the song Sudhukarn was composed in the "A B A C" form. begining with introduction of 4 bars followed by basic melody of 54 sentences, in this 54 sentences, the melodies are divided into 2 patterns : a fixed basic melody patterns of the Look-Tok and a variable basic melody patterns in between the Look-Tok. The fixed basic melody pattern is shown by the note ending of each sentence or the Look-Tok. The Look-Tok notes are fixed in 6 different notes of RE, Ml, FA, SOL, LA and Tl. All of the 10 recording samples showed the same fixed pattern of the Look-Tok. A variable basic melody patterns are found in between the fixed Look-Tok. This result in large number of variation in the song Sadhukarn which are reported in ths thesis. These variations are called the "Thang" which is a free basic melody allowing musicians to change hands and techniques according to their wit of playing. All variations were recorded in notation for detail reading. The rhythmic unit of the song Sadhukarn is called "Na-Tap" played by the Tapon (two headed hoizontal set drum) in a middle tempo one rhythmic unit is devided into 4 parts and one part is equal to one sentence long. At time of playing the Tapon will first start for 2 bars then the introduction is started then the melody of 54 sentences are followed. Several myths and stories concerning birth of this song Sadhukarn were reviewed in this study as well as function of this song used in Thai ceremonies both for the court and for the normal home life. Since the song Sadhukarn is one of the important song of the Thai classical music which is one in the group of "ceremonial music", thus, other ceremonial songs should be analysed infuture too. Gaining of the experiences in research in Thai songs and music would be great help for the better development of graduate studies in Thai music.