Particles in the solid state have least kinetic energy. This is so as they as packed very closely together and hence very less free space is available.
Liquids' particles have a slightly higher kinetic energy as they do not possess any fixed shape and have a bit more space to move around.
Finally, particles in the gaseous state have the highest kinetic energy as they have neither a definite shape nor a fixed volume. They have huge inter-molecular spaces and hence have higher kinetic energy. Further, they even possess the latent heat of vapourisation which leads to higher K.E.