I have had a couple of friends die here Pattaya who lived on their own. They weren't found for a week by friends. The police then came in and cleared our all personal belongings as there was no immediately visible last will and testament. In one case, the relatives came from the USA to show the police the will and recover his belongings. However, they never recovered his war medals which had disappeared.
In the other case, the Government took possession as nobody came to claim the body.
If you have any property in Thailand it is essential that you make a Thai will and ensure that the provisions are included in any other overseas wills.