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Natural populations of the Siamese spiny eel, Macrognathus siamensis (Günther, 1861) have drastically declined while their selling price has been rapidly increasing. For the culture of this species, knowledge of the exact duration of the stages of morphological development of the digestive system would help keepers match appropriate types of food with the changing needs of the larvae. Brood-stocks (10 pairs) of Siamese spiny eel were obtained from the Inland Fisheries Research and Development Regional Center 4 in Ubon Ratchathani Province and artificially induced to spawn by injecting buserelin acetate at 30 µg·kg-1 and domperidone at 10 mg·kg-1. After hatching, 20 fish larvae were serially sampled every two days, from 3 dph (day post hatching) to 40 dph. Fish specimens were fixed in 10% formaldehyde solution and processed for microtome study. Results showed that after hatching, the alimentary canal of the Siamese spiny eel was a straight tube, attached dorsally to the yolk sac. Differentiation of alimentary canal into buccopharynx, esophagus, and anterior and posterior intestine was found at 3 dph, along with the development of other accessory organs, such as liver, pancreas and gall bladder. During 7-9 dph, stomach divided into the cardiac, fundic and pyloric parts. At 11 dph, full development of gastric glands was found along the fundic region, as well as the appearance of the pyloric sphincter, which enabled us to discern the stomach from anterior intestine. From 13 dph until the end of the experiment (40 dph), there was no notable differentiation of the digestive tract except for increasing size. The results suggest that weaning of larvae would be appropriate at 13 dph, according to its fully developed digestive system. [ABSTRACT FROM AUTHOR]