Introduction
Payroll in Thailand is rarely “just salary.” It’s a recurring compliance cycle that touches Social Security (SSO), personal income tax (PIT) withholding, monthly filings, annual summaries, employee certificates, and (when things slip) penalties that can add up faster than most teams expect.
If you run payroll in Thailand — whether through your own entity, via payroll outsourcing, or by managing inputs under an EOR — your biggest operational risks tend to come from:
- missing a deadline by a few days (especially around public holidays),
- mis-timing payroll cutoffs vs bank processing,
- confusing paper vs e-filing deadlines,
- and underestimating how surcharges are calculated (monthly, often “per month or fraction thereof”).
This article is a 2026-focused cheat sheet that HR and finance teams can use to build a reliable monthly rhythm, including:
- key deadlines (SSO + PIT withholding),
- what to file and when,
- common penalty mechanics,
- and practical controls to prevent late filings.
The “One-Page” Cheat Sheet
Monthly deadlines (core payroll compliance)
1. Social Security contributions (SSO)
- Due: 15th of the following month
Thai Social Security Act requires employers to remit both employer and employee contributions within the 15th day of the month following the month of deduction.
2. PIT withholding on employee income (PND.1)
- Due (paper): typically the 7th of the following month
- Due (e-filing): commonly 8 days later than the normal deadline (often translating to the 15th) when the e-filing extension applies.
Thailand’s Revenue Department has extended the “8-day extension” initiative for e-filing until 31 January 2027, supporting the continued use of online filing.
A practical tax calendar example shows monthly PND.1 remittance due on the standard deadline with a later “deadline for internet filing” date.
Reality Check:
The exact due date can shift if the deadline falls on a holiday — many calendars state you can file on the next working day without being considered late.
Annual payroll items
3. PND.1 Kor (annual withholding summary)
Tax calendars commonly specify that employers must file an annual summary report on withholding from employee remuneration (PND.1 Kor).
4. Employee withholding certificate
Employers should provide employees with annual withholding certificates summarizing total income, tax withheld, and social security deductions — often issued around February in practice (timing varies by employer process).
Why deadlines slip in Thailand
Most payroll delays aren’t caused by the tax authority’s calendar. They’re caused by internal workflow issues:
- Variable pay items (OT, commissions, reimbursements) come in late.
- Managers approve late because they’re traveling.
- Finance waits for “one last correction.”
- Payroll run is pushed, then filing is pushed, then bank remittance misses a cut-off.
The fix is to treat compliance deadlines as non-movable, and build earlier internal cutoffs.
A good Thailand payroll control system uses:
- Input cutoff (e.g., 3–5 business days before payday)
- Approval cutoff (e.g., 2–3 business days before payday)
- Payroll lock (no changes after lock)
- Filing checklist (completed within 1–2 days after payroll is finalized)
1. SSO Deadlines (Contribution + Filing)
What is due & when?
Under the Social Security Act:
- the employer deducts the employee portion from wages,
- then remits both portions to the Social Security Office within the 15th day of the following month, along with the required contribution statement.
Operational Rule:
If you pay March wages in March, plan to remit SSO by 15 April.
Late payment surcharge: how it’s calculated?
The Social Security Act states that an employer who fails to pay contributions within the prescribed time must pay an additional payment at 2% per month of the outstanding contributions (with “15 days or more” counted as a month).
A tax calendar summary echoes the same principle: late remittance after the 15th is subject to a 2% per month surcharge.
What this means in practice:
- Paying even 10–20 days late can trigger a meaningful additional charge.
- “Fraction rules” can make short delays surprisingly expensive.
2026 cost driver: higher wage ceiling for SSF / SSO calculations
Starting 1 January 2026, the maximum wage base used to calculate Social Security Fund contributions increases to THB 17,500, increasing the maximum monthly contribution to THB 875 for employer and employee.
Payroll best practice for January 2026 onward:
- Confirm your payroll system updates the wage ceiling and caps correctly.
- Confirm your payslip format reflects the new cap.
2. PIT Withholding on Salaries (PND.1) — Deadlines + Rhythm
What is PND.1?
PND.1 is the monthly return used to remit personal income tax withheld from employee remuneration.
For employers, it’s the backbone filing that ties payroll to the Revenue Department.
When is PND.1 due?
Thailand uses:
- a “standard deadline” (commonly reflected as the 7th of the following month for monthly withholding filings and provider guides), and
- an “internet filing” deadline that is later when the e-filing extension applies.
Thailand’s Revenue Department has extended the e-filing + online payment deadline extension initiative until 31 January 2027.
A tax calendar example shows monthly PND.1 remittance due, with a later “deadline for internet filing” date where the filing is made online.
Practical employer takeaway
- If you e-file, you usually gain a few extra days (often translating to the 15th).
- Don’t use the extension as a habit — use it as buffer.
Internal cutoffs to hit PND.1 deadlines reliably
A workable monthly payroll timeline:
- Day 20 – 25: payroll inputs due (OT / allowances / commissions / leave deductions)
- Day 25 – 27: manager approvals
- Day 28 – 30: payroll locked, payslips prepared
- Payday: end of month or fixed date
- By Day 3 – 5 of next month: confirm withholding and prepare PND.1
- File and pay by due date: standard deadline, or internet deadline if e-filing
This rhythm avoids the “panic” filing that creates errors and late payments.
3. Annual payroll filings & year-end tasks
Monthly payroll is only half the story. Most compliance “surprises” happen during year-end because teams didn’t plan for annual outputs.
1) PND.1 Kor (annual withholding summary)
Tax calendars typically state that employers must submit an annual summary report of remuneration paid and tax withheld for employees (PND.1 Kor).
Best Practice
- Treat this as a controlled “year-end close” project.
- Reconcile payroll ledger totals to the sum of monthly filings before submitting.
2) Employee withholding certificates
Practical payroll guidance commonly expects employers to issue employees an annual certificate summarizing:
- total income paid,
- tax withheld,
- and Social Security deductions — often issued during February for current employees.
Best Practice
- Issue certificates early enough for employees to file their own annual PIT return.
- For leavers, issue within your exit process.
4. Common penalties
Penalties generally have three “families” in Thailand payroll compliance:
- Surcharges (percentage per month on unpaid tax / contributions)
- Fines (fixed amounts for late filing)
- Additional Penalties (for underpayment, inaccurate returns, or assessment outcomes)
A) Revenue Department surcharge: 1.5% per month concept
The Thailand Revenue Code includes a surcharge rule: failure to pay or remit tax within the time prescribed can trigger a surcharge of 1.5% per month or fraction thereof (with potential reduction where approved extensions apply).
Tax calendars summarize this widely: withholding income tax, VAT, PIT, and other tax types can incur a surcharge of 1.5% per month (capped at the tax payable).
Why employers should care?
- If you’re late remitting withheld PIT, your “tax cost” grows monthly.
- The surcharge is usually calculated on the unpaid amount, and the “fraction” language means even partial months can count.
B) Social Security surcharge: 2% per month (SSO)
As above, Social Security Act provides a separate surcharge: 2% per month for late SSO contributions.
C) “Late filing” fines
Some calendars and professional guides state that late filing of a tax return can result in a fine not exceeding THB 2,000.
For withholding tax returns specifically, practical guides frequently cite small fixed fines (e.g., THB 100 / 200 depending on lateness) plus the monthly surcharge.
Important:
Fine amounts and enforcement can vary by form and circumstance. Use your accountant to confirm which fine applies to which return, but design your process to avoid all of them.
5. “Failure modes” that trigger penalties
Failure mode 1: Paying salary late → rushing payroll → filing late
Fix: Set your payroll cutoff earlier and enforce “no changes after lock.”
Failure mode 2: Variable pay enters after cutoff (OT, commissions)
Fix: Set a policy: “Anything submitted after cutoff goes to next month unless CEO-approved.”
Failure mode 3: Relying on one person to file everything
Fix: Add redundancy:
- a documented checklist,
- a backup filer,
- and a monthly sign-off process.
Failure mode 4: New joiners / leavers not reflected correctly
Fix: Tie payroll to HRIS or at least a change log:
- start date,
- salary,
- SSO enrollment date,
- final pay components and certificate timing.
Failure mode 5: Holiday disruptions
Deadlines that fall on holidays can shift to the next working day without being considered late (a common tax calendar rule).
Fix: Build a “holiday-adjusted payroll calendar” each year (especially around Songkran and year-end).
6. Practical Thailand payroll calendar template
Use this internal template to align HR + finance:
Every month
- By the 20th: HR submits changes (new hires, salary changes, unpaid leave, terminations)
- By the 25th: Ops submits OT/commission/allowance inputs
- By the 27th: approvals complete
- By month-end: payslips issued + salary paid
- By the 5th: reconcile payroll to withholding and SSO contribution calculation
- By the due dates:
- SSO remittance by 15th of the following month
- PND.1 remittance by standard deadline (paper) or internet deadline (when e-filing extension applies)
Every year (Jan–Mar)
- Prepare annual payroll summary (PND.1 Kor)
- Issue employee withholding certificates (50 Tawi / 50 bis equivalent)
Conclusion
Thailand payroll compliance becomes much easier when you treat it as a system:
- SSO: remit contributions by the 15th of the following month, and remember the 2% per month late surcharge under the Social Security Act.
- PIT withholding (PND.1): follow the standard monthly rhythm, and use e-filing extension only as buffer — the e-filing deadline extension has been extended until 31 January 2027.
- Penalties: understand that tax surcharges commonly run at 1.5% per month or fraction thereof, and SSO runs at 2% per month — small delays can become expensive.
- 2026 readiness: update payroll settings for the SSF/SSO wage ceiling increase to THB 17,500 (max contribution THB 875 each for employer and employee).
Looking to hire in Thailand?
At Aster Lion, we help companies choose the model that fits their current stage — and design a transition path that avoids compliance gaps and employee disruption as they scale in Thailand.
Contact us to learn how we can simplify your hiring process.