@Nelly *****
if you are so certain, why are you asking?
The idp is valid for a longer period than 3 months (I can't remember how long 12 month's?), but it is only valid in Thailand for 3 months at a time, so if you are planning to retire here, it becomes invalid after 3 months, as everyone is stating.
Up to you if you want to risk it, as long as you don't crash into me!