Where To Get Signature To Prove Tax Liability?

Hopefully someone knows this.

I am a Danish national who have been living here for some years. I recently received a letter from the Danish tax authorities, where they request a signature from the Thai tax authority, to prove that I have paid income tax in Thailand.

I have my tax tax slips from the last few years, but I am not sure where to go to get this signature/stamp so I can verify this towards the Danish tax authorities.

I gave the Danish tax authorities a call, and they said someone who can verify my address and tax liability. Anyone knows where and who that might be?