The first question is, what are you bringing to LoS that must have a UK plug on the end of it? If the other end can be detached and has a standard IEC, cloverleaf or "Mickey Mouse" connector at the device end, you could buy a new lead with either a 2-pin European Schuko round-pin or US flat-pin plug and bring that instead. Almost all Thai sockets will accept the usual European and American 2-pin plugs.