Preterm infants are at an increased health risk due to their low maturity. To monitor their health, vital signs are measured using contact-based methods. The adhesive sensors used to detect body temperature can damage the sensitive skin of neonates. Thus, a subject of current research is non-invasive measurement methods based on infrared thermography. In this context, thermal phantoms can be used to develop contactless temperature measurement systems and, furthermore, investigate the thermal behavior of preterm infants. In this work, an improved thermal phantom is introduced to simulate the thermoregulation of a premature infant. The shape and size are adapted to the body of a premature infant in the 29th week of pregnancy. The phantom consists of a 3D-printed frame to which carbon fiber heating elements and Pt1000 temperature sensors are attached. The frame is enclosed by a thermally conductive skin layer made of a silicone boron nitride mixture. Ball joints allow the body parts to tilt and rotate, enabling the phantom to model different body postures. Using PI controllers, the thermal phantom can achieve desired temperatures in 13 different areas of the body while maintaining a homogeneous temperature distribution on the skin surface. In addition, pathological temperature scenarios such as a central-peripheral temperature difference or a change in body temperature can be simulated with a maximum deviation of ± 0.4 °C.