Contractual penalty not paid - possible consequences?

[houzi68]

Farang friend of mine, acting personally as individual, entered a purchase contract with a Thai company. The deal went through, he paid and received the goods. However that contract had a penalty clause - under certain circumstances, within 5 years after signing a contractual penalty of 100.000 Baht would be payable. These circumstances arose and the company is demanding payment of the penalty.  Farang did not pay the contractual penalty and in the meantime does not live in Thailand anymore. What can possibly happen? So far only emails have been exchanged asking for payment. Are Thai companies going to court for such amounts? Would this be a civil case under Thai law or criminal? Will immigration have him on the list when he returns to Thailand some day?

Edited March 10, 2017 by houzi68
additions