Health insurance abroad makes sense in any case.
For a regular holiday of up to 4 weeks, you pay very little for complete cover.

It starts with dental problems and ends with a traffic accident with a scooter.
In both cases you have to pay. Where the dentist is even cheaper than in Europe, the hospitals in Thailand sometimes charge crazy amounts.

Everything that requires a hospital stay is expensive. If something really happens, you dont want to worry about the bill and decide what you can afford in terms of necessary operations. Of course, no one should get hurt, but the dangerous road traffic in Thailand is known worldwide. You dont even have to drive yourself. One would have to guess, but in many road accidents pedestrians are involved or the injured parties.

If you are injured, you have to show your insurance documents. Sometimes you are not even treated if you cannot show your insurance cover. This is actually in the news from time to time.

You may already be covered abroad with your regular health insurance, but you should call in advance and ask. This is often limited in time (up to a maximum of 4 weeks) and/or in the amount when something is paid. Often only the most necessary things are covered and then in the worst case with an own contribution.