แต่ตอนเราเกิดจนกระทั่งอายุ 17ปี เราไม่ได้ถือสัญชาติไทย  So, you were/are a Dutch citizen?

Have you denounced Dutch nationality?

If not, contact the Dutch embassy, sort it out and get a new passport.

http://www.government.nl/issues/nationality/acquiring-or-regaining-dutch-nationality-while-living-in-another-country
Former Dutch nationals

Former Dutch nationals who live in another country can apply to the Dutch embassy or consulate for their Dutch nationality to be restored. Former Dutch nationals are people who once possessed Dutch nationality, but who lost it at some point, for instance as a result of acquiring another nationality. Someone who lives in the country whose nationality he possesses cannot become a naturalised Dutch national. However, women who lost their Dutch nationality as a result of marriage can opt to have their Dutch nationality restored.

As a rule, any former Dutch national who regains Dutch nationality through naturalisation must renounce his present nationality or nationalities. When a former Dutch national regains Dutch nationality by option, however, this will not generally be necessary.

The brochure issued by the IND (in Dutch) ‘Hoe krijgt u de Nederlandse nationaliteit terug?’ (‘How can you regain Dutch nationality?’ available in Dutch only) explains what former Dutch nationals have to do in order to regain Dutch nationality.

https://dloket.helmond.nl/loketburgers/gemeenteimage/Folder_NL_nationaliteit_terug.pdf

http://australia.nlembassy.org/binaries/content/assets/postenweb/a/australie/netherlands-missions/import/products_and_services/consular_services/dutch-nationality/q-a-citizenship-law---en.pdf

4. I am a Dutch citizen or at least I think I am, but I have not applied for a Dutch passport for many years. Is this a problem?

Any Dutch citizen, who is a dual national living outside the Kingdom of the Netherlands and outside of the European Union for a period of 10 years, automatically loses the Dutch citizenship unless he/she applies for and receives a valid Dutch passport at least once every 10 years or lives in the Kingdom or the EU for at least one year.
Advice: always see to it that you and and your Dutch children have valid Dutch passports. Then your Dutch citizenship is safe.


PS. I do not know much about Dutch nationality laws, only some knowledge of UK and some other European nationalities, as I have been living in Europe for many decades.