The signature of King Mongkut (r. 1851–1868) reads ''SPPM'' (''Somdet Phra Poramenthra Maha'') ''Mongkut Rex Siamensium'' (Mongkut, King of the Siamese), and the usage of the name in the first international Bowring Treaty giving the name ''Siam'' official status until 24 June 1939 when it was changed to "Thailand". Thailand was renamed ''Siam'' from 1946 to 1948, after which it again reverted to "Thailand".