It is found that age of marriage is related to fertility. The number of live births is reduced in proportion to the higher age of marriages. A higher rate of live births is related to duration of marriage. The relationship between child mortality and fertility is related to the reduction in the fertility rate. Regarding social factors, it is found that education of spouses is related to fertility. The relationship between family structure and fertility is found to be uncertain. In terms of religions, women of the Thai Mai Cult have a higher rate of live births than those of other religions. Economically, those with two jobs or more have a higher rate of live births. Those with lower income have better fertility than those with higher income. In regard to knowledge and attitude toward family planning, those practicing family planning have a lower rate of live births than those who do not. As for age, among the 15-24-year age group and those practicing family planning, the rate of live births is higher. The result is in contrast to those in the 35-44-year age group. Socio-economic and demographic differences clearly affect the fertility of those in Phuket and Phang-nga. The fertility of those in the 15-24 and 35-44 age groups in Phuket is lower than that in the other two provinces.