it worked for me about 8 years ago and then I traveled to the UK and came back and the next time I tried it it didn't work and it never has done since. When I mentioned it to an immigration office he just shrugged and laughed. The new system is also failing many people. It's hit and miss.
The ED visa is effectively no more. I just happened to watch an interview today on the Thaiger channel with a lawyer in Bangkok who said they haven't an issued one in Bangkok for a long time. Apparently now you have to get official accreditation from your university in your own country.
I've never used it but my guess is that the Wi-Fi won't be very reliable on the train. I'm just thinking about how many people would be sharing that signal. Check out DTAC because they do similar offers if you have a phone then just go to somewhere like 7-Eleven and they can top up your sim card with a data package