You should ensure that you have a last will and testament when living in Thailand. You could make a last will and testament for your assets in Thailand. You will need to speak to a probate lawyer in Thailand about this as the probate process is much easier when you do die when the assets are separated in your last will and testament.
Once you die, your family will need to find a probate lawyer to ensure that the case is filed with the courts in Thailand. Note that there is a short statute of limitation in which to file an objection to an existing estate case in Thailand. If you are a relative that has not been included then you have a short period in which to raise your objection. When you are winding up the estate all institutions, banks, Embassy as well as private and governmental agencies involved need to be notified of the death. For a foreigner, the death would need to be registered with the Embassy as they need to nullify the passport.
For foreigners it can also become more complicated when there are assets overseas. If legal action is taken in the US or the UK and an order of court has been issued then you cannot enforce this in Thailand. What you will need to do is to use this foreign court order as evidence in the Thai probate case. The court order become part of the evidence in the probate matter.
If there is no will, then as a statutory heir Thai law does not distinguish between a Thai or non-Thai. As an example, if your wife dies and leaves the house which is in her name to you, a new problem occurs. As a foreigner you are nor generally allowed to own land in Thailand. Under these circumstances normally you would have 1 year to sell the property. It could also be that you have no family in Thailand and you might leave your Thai assets to your son in your home country. Your son will then have to ensure that he is able to take over the property to get the probate lawyer to sell all the assets. Proper estate planning in Thailand is very important and it minimises the costs and legalities later if your estate has been planned properly.
Property is normally the major issue. Property leases are not inheritable and the lease is terminated at the death of the lessee, however it can be added to the original agreement that the lease is inheritable. This is why estate planning in Thailand is important. You would also have your attorney look at your usufruct which you might have as well as superficies where you own the property but not the land. All of these issues need to be looked at. If you hold certain assets in a Thai company then you will also need to view how this will be settled and the shares transferred to the heir.
Always take sound legal advice when drafting a last will and testament as probate costs can be kept low if you have planned your estate properly.