Computer simulations of a wide range of applications like materials processing, thermal energy storage and conversion systems, nuclear reactors, solar energy, and pollution control, etc. are of high importance in this era. In many of these applications, strong thermo-fluidic interactions between fluid and structures exist. Efficient and accurate numerical modelling of these interactions provide initial predictions of the process, but at times, it becomes challenging where complex shape of the structures is involved. To address this issue, often numerical methods that are proposed suffer lower computational accuracy and complex algorithms to capture interfacial predictions. In this paper, development, accuracy study and robustness of an in-house openMP parallelized Immersed Boundary-Thermal Lattice-Boltzmann (IB-TLB) solver are presented, which is capable of simulating complex boundary problems involving thermal interactions and accurately capture interfacial predictions. The solver showed excellent agreement with literature for a natural convection problem involving eccentrically placed stationary heated cylinder inside a cold square enclosure and forced convection around an iso-thermal circular cylinder. The numerical simulation of moving bodies is already quite a complex problem and the complexity increases further when we introduce heat transfer phenomena in it. Spatial order of accuracy test revealed, the IB-TLB algorithm exhibits first-order accuracy for velocity and temperature errors while pressure error retained second-order accuracy for moving boundary problems. It is also observed that the present algorithm can accurately predict local parameters like coefficient of pressure and Nusselt number with good accuracy and thus possesses promising potential to simulate complex moving boundary problems. The present solver will find its application in a wide range of areas such as heat exchangers, solar energy systems and chemical and food industries etc. © 2020 Institute of Physics Publishing. All rights reserved.