Community structure of prawns in the Tha Chin mangrove estuary, Samut Sakhon province, was investigated on bimonthly schedule of the total 7 stations from May 1997 to May 1998. Prawn samplings were conducted twice by a small push net in each sampling period during day and night. The total of 18 species from 9 genera and 5 family were recorded : Two snapping shrimp, Alpheus euphrosyne and Alpheus rapacida in the family Alpheidae. Latreutes mucronatus in the family Hippolytidae. Exopalaemon styliferus, Macrobrachium equidens (brackish water prawn), Macrobrachium mirabile, Macrobrachium rosenbergii (giant fresh water prawn), Palaemon semmelinkii (brackish water prawn) and Palaemon sewelli in the family Palaemonidae. Metapenaeus affinis (jinga shrimp), Metapenaeus brevicomis (yellow shrimp), Metapenaeus ensis (school prawn), Parapenaeopsis hungerfordi (dog shrimp), Penaeus merguiensis (banana prawn) and Penaeus monodon (giant tiger prawn) in the family Penaeidae. Three planktonic shrimp, Acetes indicus, Acetes japonicus and Acetes vulgaris in the family Sergestidae. Penaeus merguiensis (banana prawn) was the dominant group. Macrobrachium equidens (brackish water prawn) Parapenaeopsis hungerfordi (dog shrimp) and Metapenaeus ensis (school prawn) were common in respective order. Two planktonic shrimp, Acetes indicus and Acetes vulgaris were dominant in the night catches. Prawn standing crop during day and night catches were significantly different with higher values during night catches. High abundance and standing crop of prawn were found in the mangrove forest along Bang Ya-Preak coastline. Salinity was the most importance parameter determining the abundance and distribution of prawn in this area. Lowest prawn abundance and standing crop were recorded during the wet season 1997. From length frequency distribution data, most prawns were in the juvenile to matured stages. This indicates that the Tha Chin mangrove forest is the important nursery ground and shelters for prawns. From the stomach content analysis in several economically important prawns revealed that these prawns were omnivorous with detritus as their major food items. Plant materials comprised 63.74 in percentage while the animal tissues were approximately 36.26. The average C:N ratio in foods found in the prawn stomach content were 5.63. The Tha Chin mangrove forest also serves as the feeding grounds for prawn populations. These prawns showed niche partitioning in order to reduce competitions by specialized feeding. They also feed on the bottom substrate and in the water column.