The German embassy asked me for a DNA test to recognise my own son. It took four months, and for that whole stretch my son legally didn't exist for any country except Thailand.

I'm German, 41, and my Thai partner, Ploy, 29, had our son Ben at a private hospital in Bangkok. We weren't married at the time, something that in a lot of countries doesn't change the process much, but in the German case turned out to be the detail that complicated everything else.

As a father not married to the mother, Germany doesn't automatically recognise paternity just because my name appears on the Thai birth certificate. I had to legally acknowledge Ben before the German embassy, a process that, they explained, normally requires a DNA test when there's no marriage involved.

The DNA process itself wasn't technically complicated: an appointment at an authorised clinic in Bangkok, samples taken from Ben and me, sent to a certified lab in Germany for analysis. What was hard was the wait, nearly four months in total between the appointment, the shipment, the analysis, and the official confirmation.

During those months, Ben had a Thai birth certificate and nothing else. He couldn't apply for his German passport, or his consular ID number, until the paternity acknowledgment was settled, test result in hand.

Ploy took the wait more calmly than I did, reminding me several times that Ben had plenty of Thai nationality through her side and was never really going to end up without a country, though I struggled not to dwell on worst-case scenarios, especially while we were planning a trip to Germany for my parents to meet him.

When the confirmation finally arrived, with the result we expected, the rest of the process (German nationality registration and the passport) moved along fairly quickly, just a few more weeks.

Ben now has a German and a Thai passport, and met his German grandparents on a trip we took six months later than we'd originally planned. What stuck with me most from the whole experience is how important it is, for any foreign father in the same situation, to ask their own embassy from day one exactly what paternity proof they require when the parents aren't married, rather than assuming the Thai certificate is enough on its own.