You don't seem to have had much of a response here, but it's a tricky subject. I'm no expert, so I don't know if I can be much help. However, if you aren't resident in any country for more than 3 months, I don't think you will be eligible to pay taxes there. I face a similar problem myself. When I moved to the Netherlands I registered my company with the KvK and chose to pay Dutch taxes. That was two years ago. Now I'm on the move again. I was happy to continue paying Dutch taxes, but the KvK said I needed to uitschriven met mijn bedrijf because I no longer had an address in the Netherlands. I've spent some time looking into this and still have no answers, so I'm going to just keep on setting money aside (als spaargeld) so I have it if needed.
The thing is, in your case, your clients are expats. Even though they are Dutch, they probably won't be sending money from the Netherlands, so there should be nothing to muddy the water and make things overly complicated. In theory you may not have to pay taxes at all.
Actually we appear to be in the same boat. I'm an Englishman who made everything "legal and transparent" and began paying Dutch taxes—for two years. Your a Dutch man who chose to pay Thai taxes—for two years. We've both now moved on are wondering what the f@@k we're meant to do. Een beetje van een toeval, toch?
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