For the vast majority of reptiles, low temperature is a major constraint on reproduction. However, continuous reproduction is not always observed even in equatorial climates. In the present study, we examined the reproductive output of green turtles in a year-round nesting population on Huyong Island, Thailand. From 1996 to 2007, 121 females were identified. Because individual turtles nest several times within a season, we defined the nesting season of an individual as the month during which the first nesting activity was detected. We found a significant difference in clutch frequency among months. However, there were no significant relationships during the nesting period between clutch frequency and environmental parameters such as mean daily air temperature, precipitation and maximum wind speed. Although we could not identify the specific factors, our findings suggest that environmental factors may regulate seasonal variation in reproductive output even in the tropics.