Thailand has had rapidly and substantially declining fertility during the last three decades. At present, the total fertility rate (TFR) of Thailand is below replacement level; however, the fertility decline was uneven throughout the country. Fertility differentials levels have remained the same in the provincial and regional areas. Some provinces have shown high levels of TFR, especially the provinces where ethnic minorities live. The main objective of this study is to estimate level and pattern of fertility of three ethnic groups namely the Khmer-Suay, Malay speaking groups and hill tribes. Data used in this study are from a one-percent sample of a census of Thailand conducted in 2000 by the National Statistical Office (NSO). The language primarily used in a household was used to classify the ethnic group of the samples. An indirect method introduced by Palmore in 1978, developed from Bogue-Palmore (1964) is used to estimate fertility rates. This method requires the ratio of children to women of reproductive age, infant mortality, mean age at first marriage and proportion of married women by age to estimate fertility. These data are calculated directly from the census. The exceptions are infant mortality rate and median age at first marriage that can not be obtained directly from a census. Therefore, infant mortality was indirectly estimated using Trussell’ s method, adjusted by using infant mortality rate from the 1995-1996 Survey of Population Change (SPC) as a standard. Separate mortality estimates were calculated for each ethnic group. The median age at marriage was estimated by using Hajnal’s method. The results show that TFRs for Hill tribes, Malay speaking groups and Khmer-Suay are 3.4, 2.9 and 2.4 respectively. Fertility of these three minority groups are above the replacement level and higher than the TFR of the overall Thai population. However, the fertility levels and patterns are still substantially different between minority groups. This may be because of the relationship between levels of infant mortality and fertility as well as effects of socio-economic status, cultural and religious belief.