The present study was conducted to optimize stocking density of Thai Koi (Anabas testudineus) in monoculture for a period of 98 days in 6 ponds of 0.2 ha each in a commercial farm under Mymensingh district. Three stocking densities of Thai Koi at 74,100, 86,450 and 98,800 ha-1 were assigned to treatments Ti, T2 and T3, respectively. Each treatment had two replicate ponds. The mean initial weight of Thai Koi was 0.2 g. A pelleted commercial diet containing 32-35% protein was fed twice daily at the rate of 20, 15, 12, 10, 8, 5 and 4% of the total body weight of the fish which was adjusted fortnightly. Feed conversion ratio (FCR) ranged from 1.73 to1.94 among the treatments. The water quality parameters were measured fortnightly and the ranges of temperature, pH, dissolved oxygen and total alkalinity were 27.5-29.6°C, 7.8 - 8.7, 5.1-6.2 mgC and 101-144 mgl..", respectively. Percent survival (%) of Thai Koi varied from 82.03 to 90.47. The weight gain of Thai Koi in Ti (91.0g) was significantly higher (P<0.05) compared with that of T2(84.1g) and T3(76.5g). This result indicated higher growth in weight (g) at lower stocking densities and the growth rate gradually decreased with increasing density. The Specific Growth Rates (SGR %) were 6.73, 6.60, 6.54 in T1, T2 and T3 respectively and demonstrated no significant difference (P>0.05) among the treatments. The achieved production in weight were 6,584.84, 6,388.29 and 5,700.31 kgha-lin T3, T2 and Ti, respectively. The production of Thai Koi was significantly higher (P<0.05) in T3 than those the T2 and Ti. But the highest net profit (Tk. 109.35 kgfish-1) was derived in Ti and lowest (Tk. 77..90 kgfish-1) in T3. The investment was rather highest in T3(Tk. 72.09 kgfish-1) and lowest in T1 (Tk 60.65 kgfish-1). That means the market value of per kg fish is decreasing in higher stocking density than the lower stocking density for its individual weight. Therefore, from the results of this study, it is concluded that for higher profit a total stocking density of 74100 ha "1 for Thai Koi (Anabas testudineus) monoculture in pond aquaculture system may be recommended.