Over the past several years, there have been numerous cases where car insurance companies have denied compensation on the grounds that the driver’s blood alcohol concentration (BAC) exceeded 50 milligrams percent at the time of the accident, the legal limit under the Land Traffic Act B.E. 2522 (1979).

However, what has caused serious unfairness to consumers is that some insurance companies retroactively calculate alcohol levels without relying on the actual test results taken at the time of the incident. Instead, they use internal calculation manuals, assuming that the alcohol level in the blood decreases by 15 milligrams percent per hour, then use this formula to conclude that the insured person must have exceeded the legal limit at the time of the accident.

This practice raises a serious legal and ethical question:

“Do insurance companies have the legal right to retroactively calculate alcohol levels on their own?”

The Law Is Clear: Only the Actual Alcohol Level at the Time of the Accident Matters

According to both insurance policy terms and Section 43(2) of the Land Traffic Act:

“If the driver has a blood alcohol level exceeding 50 milligrams percent at the time of the incident, it is considered a violation of the law.”

Therefore, determining whether the driver exceeded the legal limit must be based on actual test results taken at the time of the accident, or as close to that time as possible not on retroactive estimations or assumptions derived from internal company guidelines.

Hence, when an insurance company unilaterally interprets that retroactive calculation is valid, it violates the insurance contract and potentially exploits consumers, lacking credible scientific evidence.

The Court of Appeal’s Judgment: Retroactive Calculations Are “Unreliable”

In one case handled by Wongsakorn Law Office, the Consumer Case Division of the Court of Appeal ruled decisively on this issue.

The Court stated that the insurance company’s reliance solely on its internal policy interpretation manual, which claimed that alcohol decreases by 15 milligrams percent per hour and then retroactively calculated the driver’s BAC to exceed 50 mg%, was weak and unreliable evidence.

The Court held that such retroactive estimation represents a one-sided interpretation by the insurance company and unfairly disadvantages the consumer, violating the principles of fairness in consumer contracts.

Therefore, the Court established a key principle:

“If an insurance company claims the driver exceeded the alcohol limit, it must provide clear, impartial, and credible evidence, not merely internal calculations.”

In other words, without actual medical or police test results taken at the time of the incident, the insurer cannot deny coverage.

The Bigger Problem: Why Doesn’t the OIC Penalize Insurers?

Even though the Court of Appeal has already set a clear legal precedent, in practice, when consumers file complaints with the Office of Insurance Commission (OIC) after being denied compensation due to “retroactive alcohol levels,”
Many cases show that the OIC still sides with the insurers without thoroughly verifying the facts.

Lawyer Arm questioned:

“When the court has already ruled that the insurance company was wrong, why doesn’t the OIC penalize them?”

This highlights a major gap in the regulatory system, allowing insurers to continuously take advantage of consumers even under the oversight of the very agency meant to protect public rights.

What Should Consumers Do If Denied Compensation Due to “Retroactive Alcohol”?

Do not hesitate to consult a lawyer.
If an insurance company denies your claim on the grounds that you “had alcohol in your system while driving,” consult a lawyer immediately.

Many people mistakenly believe, “If I just explain the truth, they’ll understand,” or “I already have hospital test results; that should be enough.”
In reality, insurance companies have teams of lawyers who know every legal loophole, interpret contracts strategically, and rely on the fact that most consumers are afraid to sue.

Without a lawyer who understands insurance law and strategy, you will never outsmart the insurance company, and you will inevitably be taken advantage of.

Every word in the policy and every number in the alcohol test report can be used as a basis to deny responsibility. Some insurers even use vague terms such as “having alcohol in the blood” without specifying that the level must be measured at the time of the accident, leaving room for manipulative interpretations.

Not Supporting Drunk Driving But Also Not Supporting Corporate Exploitation

Lawyer Arm emphasizes:

“We do not condone driving under the influence of alcohol, but we also do not support insurance companies exploiting the public.”

Retroactively calculating alcohol levels not only breaches the insurance contract but also creates a dangerous precedent for consumer protection in Thailand. It allows insurers to deny compensation under virtually any pretext.Therefore, if you or someone you know has been denied coverage due to “retroactive alcohol,”
Don’t stay silent consult a lawyer experienced in consumer and insurance law to ensure your rights are fully protected.

The insurance company always has a lawyer on their side. What about you — Do you have a lawyer?

If your insurance company denies your claim using “retroactive alcohol” as an excuse, don’t waste time trying to handle it alone because ultimately, the insurer will use the law to their advantage.

Consult an experienced insurance lawyer immediately. A skilled lawyer will strategically structure your case from the beginning, ensuring that your legal rights are preserved.

Retroactive alcohol results are not legally valid evidence.

Insurance companies have no right to use such calculations to deny compensation.
If you’ve been unfairly treated, the law is on your side and having a lawyer by your side is the strongest protection you can have.

📞 For legal consultation: 062-195-1661 or click Contact Us to get immediate assistance.