Or maybe not. Its a 5 year multi entry visa, 180 days per stay, with one time extension of 180 days. Its still a tourist visa, and will not accrue towards permanent residence. And more that 180 days per year in Thailand, and you are paying Thai tax.
Obvioudly yoi misunderstand me since English is not your native tongue, explaining your unreasonable responses to some reasonable points put to you. You don't have a visa to extend. Visa exemption means no visa. Visa exemption was created to facilitate ease of travel for the majority of visitors, ie people travelling for usually 30 days or less, which is the maximum period in one country for most travel insurance schemes, and people with gainful employment in their own countries. The extension to visa exempt status is for people who's plans change for unexpected purposes. Of course, there are many people who play the system (and it is abuse of a system that is usually more liberal than where they come from), but they keep those plans to themselves. The stupid ones fess up to IOs then go whinging on Facebook about their rights. Some call them barrack room lawyers. Its not usual in most European countries to try and extend a holiday visa in country. That's usually a red flag for illegal activity, for people with no clear source of income.
This is the root problem. This concession is described as temporary, and it may not happen. The OP think it's going to happen, for the IOs, it hasn't happened.
But you suggested to them you were prepared to misuse or game the system. The 60 day visa exists for those who intend to stay in Thailand for 60 days. The 30 day visa free concession is for those who intend to stay no more than 30 days in Thailand. The extension is a further concession for those who's travel plans change while in Thailand. Essentially you presented yourself as dishonest, because with a plan to stay 60 days, you should have had a visa. Now perhaps you saw that as pure semantics, but from the IOs point of view, whether Thai or Dutch, foreigners don't have an absolute right to enter. Of course Schengan has blurred all of that. But there are still rules: EU citizens can be deported from eu countries if they no longer meet the rules of residence.
Possibly because you are spending more than 180 days a year in Thailand, so would be considered a tax resident, and may be required to pay taxes on your foreign sourced income and savings.