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.

The maximum number of working hours of employees in Thailand is fixed at 8 hours a day and 48 hours a week in total. In some types of works, as stipulated by the Thai labor law, the employer and the employee may agree to arrange the period of working hours but the working hours in any case must not exceed 48 hours a week. In establishments in which the work is deemed injurious to health or personal safety, as stipulated by law, working hours must not exceed 7 hours a day and 42 hours a week in total.

All employees are entitled to a daily rest period of at least 1 hour after working for 5 consecutive hours. The employer and the employee may arrange the daily rest period to be shorter than 1 hour at each time but it must not be less than 1 hour a day in total. A weekly holiday of at least 1 day a week at intervals of a 6 day period must be arranged for the employee.

For work performed in excess of the maximum number of hours fixed either by regulation or by specific agreement (if the latter is lower), employees must be paid overtime compensation. The rates of overtime vary ranging from 1.5 times to 3 times the normal average hourly wage rate for the actual overtime worked. Certain employees engaged in employment related work on behalf of the employer and other types of work as prescribed by law are not entitled to overtime compensation. The maximum number of overtime working hours is limited to not more than 36 hours a week.

All employees are entitled to unlimited sick leave, but the number of days paid sick leave shall not exceed 30 regular workdays a year. The employer may require an employee to produce a certificate from a qualified doctor for a sick leave of three days or more.

A female employee is entitled to maternity leave for a period of 90 days including holidays, but the number of days paid leave shall not exceed 45 days.

An employee who has worked consecutively for one year is entitled to at least 6 working days of paid vacation every year, in addition to the 13 holidays in a year traditionally observed in Thailand.

Here is the full version of Labour Protection Act B.E. 2541 (A.D. 1998)

and Labour Protection Act B.E. (No.2) 2551 (A.D. 2008)