Considerable effort has been invested in providing thermal comfort in tropical humid regions by increasing natural indoor air movement. This paper presents the result of investigation on the combined effect of balcony, opening design and internal division on the indoor airflows pattern of a living zone located on the second floor of a two storey building. The experiment was carried out by using the N3S software at the CERMA Laboratory, Ecole d'Architecture de Nantes, France. To observe the flows pattern inside buildings, we used the local average velocity coefficient as a function of the position in horizontal sections of 1.00 and 1.50 m in heights, for activity with sitting and standing position. The average velocity coefficient was calculated according to number of the measurement points in the living zone. The results identify opening and balcony designs to be helpful in increasing natural indoor air movement but not for internal division modification and they must be taken into consideration on designing dwelling in tropical humid region.