Can an employer move existing staff to part-time work without ending their employment?

Part-time conversion is often used as a cost-saving alternative to redundancy.

Commercially, the proposal may sound simple:

“Work three days instead of five and receive a proportionately lower salary.”

Legally, several things are changing at once: working schedule, pay, benefits, service continuity and sometimes status in payroll or insurance schemes.

A business has reduced demand but wants to retain experienced employees.

It proposes converting selected full-time employees to permanent part-time schedules.

Management asks:

“Can HR just issue new part-time letters from next month?”

Not if the letters reduce existing employment conditions without agreement.

Thai labour cases have treated detrimental unilateral changes in employment conditions as invalid where employees did not consent.

The employer’s general management power does not automatically allow it to impose materially worse terms.

Do not start paying the reduced amount first and ask the employee to sign later.

The document should preserve the original service date.

Creating an artificial break merely to reset accrued rights can create additional labour-law risk.

Check leave, insurance, service charge, incentives, meals, transport, social security and any other recurring benefit rather than using a blanket sentence that “all benefits become part-time.”

The proposed pay basis and schedule still need to comply with applicable wage, working-time, holiday, leave and social-security rules.

The employer may keep the existing terms, negotiate an alternative or, if there is a genuine business restructuring, consider a separate lawful termination route with the applicable notice, severance and other consequences.

The employee should be able to see exactly which period is paid under the old terms and which under the new terms.

We review the current contract, work rules, weekly schedule, salary and benefits, original service date, proposed part-time terms, minimum-wage implications, social-security treatment, payroll cut-off, amendment form and the employer’s alternative if consent is not obtained.

Typical mistakes are issuing a unilateral “part-time notice,” resetting service to zero, reducing pay before signature, leaving benefit treatment unresolved and treating refusal to accept worse terms as disciplinary misconduct.

Use a conversion schedule:

current days / hours → new days / hours → current pay → new pay → each benefit → service date preserved → effective payroll date → employee consent

Nothing should change in payroll until the legal and operational columns match.

• Labour Relations Act B.E. 2518 (1975), including the framework governing conditions of employment and collective changes where applicable.
• Labour Protection Act B.E. 2541 (1998), including section 20 on artificial interruptions intended to deprive employees of statutory rights.
• Supreme Court Judgment No. 7238/2544, on a detrimental unilateral salary and position change without employee consent.
• Supreme Court Judgment Nos. 2019–2022/2523, on an employer being unable to impose a detrimental change to shift-working conditions without employee agreement.
• Supreme Court Judgment No. 4030/2561, on the limits of management power where a transfer or reassignment is detrimental to the employee.