This aim to calculate Ångström turbidity coefficient in the atmosphere of Thailand. Its value is derived from solar radiation data for three years between 2011-2013, which relate to visibility data. The result shows that Ångström turbidity coefficient is inversely proportional with the visibility data. Moreover, the value variation is depended on time period of the year. High value was present from November to March whereas it trend to decrease during April to October. The average value varied between 0.171 0.0016 and 0.253 0.0013, the average annual is equal to 0.211 0.0024.