Lower and Middle Ordovician conodonts from the Thung Song Group, in the Thung Song and Thung Wa areas of southern peninsular Thailand, are described and illustrated here for the first time. These conodonts are divided into faunas A, B, and C, which are middle to late Arenigian, middle Arenigian to Darriwilian or Caradocian, and late Arenigian to early Caradocian, respectively. Fauna A resembles faunas in Australia, South China, the Argentine Precordillera, and North America. Fifteen species belonging to twelve genera were studied systematically.