Setting up a factory in Thailand goes well beyond finding land and purchasing machinery. Foreign and local investors alike must navigate Thai industrial, environmental, and safety regulations — and in many cases, secure a Factory Operation License (Ror Ngor 4) before operations can begin.
This guide explains the key legal requirements, licensing categories, required documents, and practical steps involved in obtaining a factory license in Thailand. Whether you are planning a new facility or expanding an existing one, understanding these requirements early can save significant time and cost.
Key Takeaway: Not every factory needs a full license — but those that do must obtain one before starting operations. Getting the classification right from the start is critical.
Understanding the Factory Act and Factory Definition in Thailand
The Thai Factory Act B.E. 2535 (1992) is the primary law governing how factories are established, expanded, and operated in Thailand. It covers licensing, safety standards, pollution control, and government supervision.
The Act is administered mainly by the Department of Industrial Works (DIW) under the Ministry of Industry.
What Counts as a “Factory” Under Thai Law?
Under the Factory Act, a “factory” generally refers to any premises where machinery of a certain total horsepower — or a specified number of workers — is used for activities like producing, assembling, packing, repairing, storing, or destroying goods that fall under listed industrial categories.
Importantly, not every site that meets this definition requires a full license. Some only need to notify the authorities, while others must obtain full approval before operations can begin. The distinction depends on the type and scale of the factory.
Factory Categories and Licensing Requirements
Ministerial regulations assign each manufacturing activity to one of three categories, and the category decides what you must do before you operate:
Category 1: No Licence and No Notification
These factories may begin operating without a licence and without notifying the authorities.
Category 2: Notification Required
These factories must notify the official before beginning operations. No licence is issued.
Category 3: Factory Operation License Required (Ror Ngor 4)
Larger factories that exceed thresholds for machinery power and number of employees must obtain a Ror Ngor 4 license from the Department of Industrial Works before commencing operations.
In some cases, operators may be allowed to start construction based on a preliminary certificate while the full license is still being processed.
Note: Factories in Category 3 must typically inform officials before conducting test runs, and again before beginning full commercial operations.
Why the Ror Ngor 4 Factory License Matters
If your project falls into Category 3, the Ror Ngor 4 factory license is a legal prerequisite to operate. Without it, the business faces potential orders to suspend operations, fines, or other enforcement measures.
The licensing process typically involves:
- Preparing a complete factory license application
- Submitting a factory layout and site plan
- Submitting a machine list and related technical information
- Providing company and land documents
- Undergoing site inspections by government officers
- Where needed, a review of environmental impact and safety measures
Because technical, environmental, and legal issues are all interconnected, most investors find it more efficient — and less risky — to handle everything through a coordinated team of lawyers and licensed engineers.
What a Factory License Application Involves
Applying for a Ror Ngor 4 license is a multi-step process that requires coordination between legal, technical, and environmental disciplines. Here is what to expect:
1. Factory Layout and Site Plan
A detailed factory layout must show buildings, production lines, utilities, access ways, storage areas, and safety systems. This plan is typically required to be prepared or certified by a licensed Thai engineer.
2. Machinery List
Applicants must submit a comprehensive list of all major machines and equipment, indicating type, power, and capacity. This information feeds into the regulatory assessment of whether the factory exceeds licensing thresholds.
3. Environmental and Safety Plans
Depending on the type and scale of your factory, you may need to provide:
- Wastewater treatment and discharge plans
- Air emissions control documentation
- Solid waste management procedures
- Hazardous substance handling protocols
- Fire safety and evacuation plans
4. Company and Land Documents
Standard supporting documents include:
- Company registration documents or affidavit
- Land title deed, lease, or other land-use documents
- Application forms and supporting statements required by the DIW
5. Operating in an Industrial Estate
Many investors choose to locate factories inside a Thai industrial estate, where zoning, utilities, and infrastructure are designed for industrial use. Estates may be operated by the Industrial Estate Authority of Thailand (IEAT) or private developers.
While industrial estates can simplify certain aspects of factory setup, they come with their own rules on land use, construction, environmental controls, and estate fees. It is important to review estate-specific requirements alongside the standard licensing process.
Good to know: You do not have to be in an industrial estate to get a factory license. Many licensed factories in Thailand operate on standalone sites outside of estates.
Timeline: How Long Does It Take to Get a Factory License?
Once your application is submitted, a government officer will typically visit the site to inspect the factory area, equipment, and pollution-control systems. A report is then prepared and forwarded to the relevant industrial office.
There is a statutory timeframe for authorities to consider the application and issue a decision. However, in practice, additional questions, document revisions, or environmental reviews can extend the process.
Practical tip: It is wise to allow several months in your project timeline for the licensing process. Having complete and well-prepared documentation from the start is the single most effective way to reduce delays.
How Long Does a Factory Licence Last?
A Category 3 factory licence issued today does not expire. The Factory Act (No. 2) B.E. 2562 (2019) repealed sections 14 and 15 of the Factory Act B.E. 2535 (1992) — the provisions that fixed the licence term at five calendar years and set out the renewal procedure. Since that amendment came into force on 27 October 2019 there is no renewal application and no expiry date on the licence.
What replaced renewal is an annual obligation, not an annual application.
- Annual operating fee. Under section 43, operators of Category 2 and Category 3 factories pay an annual fee for as long as they operate, at the rates prescribed by ministerial regulation. The fee falls due on the anniversary of the date operations began, not on a fixed calendar date, and late payment carries a surcharge of 5% per month. Factories in Bangkok pay the Department of Industrial Works; factories elsewhere pay the Provincial Industry Office.
- Annual operating data return. Category 2 and Category 3 factories in the prescribed categories file their annual operating data on Form Ror Ngor 9 by the end of April following the reporting year. Where the monthly return applies, Form Ror Ngor 8 is due by the 10th of the following month.
A licence that does not expire is not a licence that looks after itself. It remains subject to the conditions on its face, to inspection, and to suspension or revocation for non-compliance.
Which Authority Decides
Outside an industrial estate, a Category 3 application is filed with the Department of Industrial Works for factories in Bangkok, and with the Provincial Industry Office for factories elsewhere. DIW retains national policy, technical and registry functions.
Inside an industrial estate, the Industrial Estate Authority of Thailand governs. An operator there does not ordinarily hold a Ror Ngor 4 at all — it holds an IEAT permission to use land and operate a business in the estate. IEAT still takes technical opinions from DIW on certain factory categories, and those opinions become conditions of the permission.
Supervision of Category 1 and Category 2 factories was devolved to local administrative organisations by the Factory Act (No. 3) B.E. 2562. Category 3 was not devolved.
Environmental and Safety Compliance
Thai regulations require all factories to operate safely and minimize environmental impact. Depending on the type and scale of your factory, key obligations may include:
- Waste and emissions control — proper treatment and discharge of wastewater, control of air emissions, and solid waste management
- Hazard and pollution prevention — systems to manage hazardous substances and reduce the risk of leaks, spills, or accidents
- EHIA (Environmental Health Impact Assessment) — for projects considered to have significant environmental impact, an EIA may be required before approval
- Safety measures and training — fire protection systems, emergency exits, evacuation plans, and regular staff training
Understanding and integrating these requirements into your factory design from the early planning stage can significantly reduce compliance risks and costly redesigns later.
Frequently Asked Questions About Factory Licenses in Thailand
Who needs a Factory Operation License (Ror Ngor 4)?
Factories that exceed specified thresholds for machinery power and number of employees, and that fall into certain industrial categories, must obtain a Ror Ngor 4 license before starting operations. Whether your project meets these criteria depends on your industry, process, and scale — it should be checked on a case-by-case basis.
How long does it take to obtain a factory license?
If documents, factory plans, and environmental measures are complete, the authorities are expected to inspect the site and issue a decision within legally prescribed timeframes. In practice, additional questions or document revisions can extend the process, so it is wise to allow several months in your project planning.
How long is a factory licence valid?
It does not expire. The Factory Act (No. 2) B.E. 2562 (2019) repealed the five-year term and the renewal procedure, with effect from 27 October 2019. What remains is the annual operating fee under section 43 and the annual operating data return on Form Ror Ngor 9.
Do I have to be in an industrial estate to get a factory license?
No. Many licensed factories operate outside industrial estates. However, estates can simplify infrastructure, utilities, and certain zoning requirements. The best choice depends on your industry, logistics, cost profile, and long-term strategy.
Why do I need a licensed engineer for factory plans?
Authorities rely on technical documents — layout plans, machinery lists, and safety systems — to assess compliance with the Factory Act and environmental regulations. These documents are usually required to be prepared or certified by licensed engineers who take professional responsibility for their accuracy.
Can I start construction before getting the license?
In some cases, operators may be allowed to begin construction based on a preliminary certificate while the full Ror Ngor 4 license is still under consideration. However, this depends on your specific situation and should be confirmed with the relevant authorities.
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Navigating the factory licensing process in Thailand requires coordination between legal, technical, and environmental disciplines. Getting it right from the start — with proper documentation, compliant factory layouts, and clear communication with the authorities — is the most effective way to avoid delays and costly surprises.
At Lex Bangkok, we work closely with licensed Thai engineers (30+ years’ experience) to provide integrated legal and technical support for factory projects in Thailand.
Our factory license and industrial services cover everything from feasibility studies and factory layout preparation to Ror Ngor 4 licensing, EPC coordination, and ongoing regulatory compliance.
Disclaimer: The information in this article is for general guidance only and does not constitute legal advice. Each project must be assessed on its specific facts. Consult a qualified Thai lawyer before making decisions.
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