According to the Thai labor law, if an employment contract does not specify any duration, either party can terminate the contract by giving notice at or before any time of payment, to take effect in the next pay period.
In Thailand, an employer does not have to pay severance pay to an employee when employment is terminated upon any of the following conditions:
(1) performing his/her duty dishonestly or intentionally committing a criminal offence against the Employer;
(2) willfully causing damage to the Employer;
(3) committing negligent acts causing serious damage to the Employer;
(4) violating work rule, regulation or order of the Employer which is lawful and just, and after written warning having been given by the Employer, except for a serious case with no requirement for the Employer to give warning.
The written warning shall be valid of not exceeding one year from the date when the employee commits the offence;
(5) absenting himself/herself from duty without justifiable reason for three consecutive working days regardless of whether there is holiday in between;
(6) being sentenced to imprisonment by a final court judgment.
In item (6), if the imprisonment is for offences committed by negligence or a petty offense, it shall be the offense causing damage to the Employer.
Upon termination of employment without severance pay upon the above conditions, the Employer needs to specify the fact which is the cause of termination in a letter of termination of employment or inform the cause of termination to the employee at the time of termination of employment.