Is it possible that children of a Thai mother inherit land and house which was owned by her, when they are not Thai citizens? If it is possible do they have the same rights like a Thai owner?

If they have a Thai parent they are automatically Thai. You should get them their Thai birth certificates and passports ASAP. If born outside Thailand you need to do this at the Thai embassy in their country of birth.

There is absolutely no reason whatever that they could not inherit land etc, but to reduce issues with inheritance there should be a will granting them the land.

If they have a Thai parent they are automatically Thai. You should get them their Thai birth certificates and passports ASAP. If born outside Thailand you need to do this at the Thai embassy in their country of birth.

There is absolutely no reason whatever that they could not inherit land etc, but to reduce issues with inheritance there should be a will granting them the land.

The mother passed away unexpected so there is no will. They are both older than 20 years and maybe their birth was never registrated with the Thai Embassy. They will have for sure a German birthcertificate where the Thai is registrated as the mother. Could that be enough?

I'm going to move this to the visas forum where it will get better exposure to the experts on dual-nationality.

I've edited the topic sub-heading to clarify that the children have a Thai parent but no Thai passports as yet.

Assuming the mother was in Thailand when she passed-on speed will be of the essence as inevitably in this situation every man and his dog will be looking for a slice of the cake

If the mother was Thai at their birth, the children are automatically Thai citizens and can inherit land, etc. (Even if they were not Thai, they could inherit, but would have to sell it within 1 year).

In your case, a Thai birthcertificate must be acquired from the Thai embassy in Berlin. That the mother is deceased complicates it a bit, but in the end it should work out all right. Best is to contact the Thai embassy and see which documents they will require in this case.

As said, speed is important.

As I understand the inheritance law in Thailand, a foreigner can inherit land etc but then has twelve months to sell it, I would suggest some very quick legal advice so the estate does not "disappear" to other family members. Getting a Thai birth certificate and passport is going to take time I would think given their ages and providing proof.

Somebody needs to notify the Thai Probate Court or contact a probate lawyer ASAP and establish an inheritance claim.