Since the first February 2016, there is a new inheritance tax and gift tax in Thailand. Before that, there was none. In summary:
"The inheritance tax is 5 per cent for ascendants or descendants and 10 per cent for others. It is levied on assets worth above Bt100 million, a loosening of the previously planned threshold of Bt50 million and tax of 10 per cent. The tax is levied on heirs who are either individuals or Thai juristic persons."
Have a look at the following article for more information: