I just returned from Hua lamphong. They still run the ticket office and some trains depart from there. If somebody here wants to drive to surat Thani by train. The departure station here in Bangkok is bang bamru.
Apply at least one week before flight just to be safe. But you can apply anytime. Technically there is no expiring date because the Thai pass is tied to your date of arrival.
I arrived here on 2nd February, booked my flight back in November and the Thai pass was approved within a few hours.
I guess you are German? I had almost the same thing (I was entering with tourist visa). After o uploaded everything needed (visa request, flight , hotel, etc) my coe was rejected. I had to go to the ambassy with all the paperwork and then it took 5 minutes to get the visa...