Not sure what the Immigration connection here is since, despite the claim of the Big C Extra facility to provide a one-stop service, you will, in practice, presumably need to toddle off to Immigration after obtaining your EEC Work Permit for the appropriate EEC Visa in your case: https://www.siam-legal.com/thailand-law/eastern-economic-corridor-eec-visa/ And by Immigration it looks likely that this means the Rayong office, despite the fact that the EEC also covers the Chachoengsao & Chonburi provinces, judging from the overcrowding issues at that particular office, which, ironically, have got markedly worse since its relocation last October!
