Patent Infringement: What to Do First

First, Document Everything

Before contacting the alleged infringer or taking any action, the most important thing is documenting evidence systematically - evidence with a clear, early date carries more weight than evidence gathered later:

• A sample of the suspected infringing product, along with a receipt or proof of purchase showing the date and source
• Photos of the product, packaging, and labeling from every relevant angle
• Advertising or marketing materials that show or reference the suspected product
• Whatever you can identify about the manufacturer or seller
• A claim chart comparing the suspected product against each claim of your patent, to show how it matches or comes close to your patent's scope of protection

For a process patent, the Patent Act B.E. 2522, Section 77 provides an additional evidentiary advantage: if the patentee proves the alleged infringer's product is identical or similar to the product obtained through the patented process, the law presumes that the alleged infringer used the patented process, unless they can prove otherwise. This significantly reduces the patentee's burden of proof in process-patent cases, which are otherwise hard to prove directly.

Cease-and-Desist as a Common First Step

Patent law does not require sending a cease-and-desist letter before filing suit. In practice, though, many patentees choose to send a formal letter first, notifying the alleged infringer of the existing patent and demanding they stop. The upside is that some infringers stop immediately once formally notified, saving time and cost compared to filing suit right away. The Patent Act B.E. 2522, Section 35 bis also gives written notice a specific legal role in one narrower situation: infringement that occurs before the patent is granted (during the period after the application is published but before grant) - if the person acting knew of, or was informed in writing of, the pending application, the applicant becomes entitled to damages from that infringer once the patent is granted. Sending a cease-and-desist letter after the patent has already been granted, however, is a practical strategic choice, not a legal requirement, and should be weighed case by case - in some situations, advance notice can give the alleged infringer a chance to prepare a defense or destroy evidence.

When Litigation Becomes Necessary

If a cease-and-desist letter doesn't work, or the situation is urgent, the patentee has the following statutory rights:

• Injunction (temporary or permanent) - Section 77 bis lets the patentee petition the court to order the infringer to stop or refrain from the infringing act, where there is clear evidence that infringement is being or is about to be committed
• Damages - Section 77 ter empowers the court to award damages in an amount it deems appropriate, taking into account the gravity of the injury, including lost benefits and the costs necessary to enforce the patentee's rights
• Confiscation or destruction of infringing goods - Section 77 quarter requires that infringing goods in the infringer's possession be confiscated, and the court may order their destruction or other measures to prevent further distribution
• Criminal penalties - Section 85 states that anyone who commits an act under Section 36 without the patentee's permission is liable to imprisonment of up to 2 years, a fine of up to THB 400,000, or both. This is a separate track from the civil case, with a different process and outcome - a criminal penalty falls on the infringer, it isn't compensation paid directly to the patentee

This article does not state specific litigation timelines or court fees, since these vary case by case and fall outside what the Department of Intellectual Property publishes. Ask a lawyer or the Central Intellectual Property and International Trade Court directly for exact figures.

What the Process Generally Looks Like

Patent infringement cases in Thailand are heard by the Central Intellectual Property and International Trade Court, a specialized court dedicated to IP and international trade disputes. The process generally starts with filing a complaint along with evidence; if you're seeking a temporary injunction while the case is pending, that typically requires a separate petition. The case then proceeds through trial, which includes presenting technical evidence to establish whether the accused product matches the patent's claims. Actual timelines and costs vary widely case by case, depending on technical complexity and how the other side responds, so a general article like this one cannot state a fixed timeframe.

Working with a Patent Agent vs. a Litigator

Responding to patent infringement usually requires both technical expertise (to compare the suspected product against your claims) and litigation expertise. Patent To You's team advises from the initial assessment and evidence-gathering stage through to direct court representation - not simply referring you to an outside law firm. That said, every case's outcome depends on its own specific facts and evidence; no result can be guaranteed in advance for any case.

Frequently Asked Questions