Another gem from the old news reports of the National News Bureau of Thailand. According to this one from June 2004 the area of Laem Chabang was planned to become another special administrative area same as nearby Pattaya.
While Pattaya was made a special administrative area in 1978 in order to make the administration more able to cope with problems from the strong growth of tourism in the town, Laem Chabang is an industrial center and especially the main port of Thailand. However, this proposal obviously wasn't successful, but I haven't seen any report on why it was dropped or at least postponed.
Laem Chabang thus still is a subdistrict municipality (เทศบาลตำบลแหลมฉบัง), and is somewhat special is it one of the very few municipalities which cover area from more than one district. It covers parts of subdistrict Bang Lamung in Bang Lamung district, and of Si Racha district the complete subdistricts Bueng, Sura Sak, Thung Su Khla and parts of Nong Kham. And despite the fact that it already has a high enough population and probably also enough tax income, it is still at the lowest municipality level.