This seems to be a recent change and comes directly from the website - SAME DAY VISA SERVICE WHEN APPLYING IN PERSON IS NOW AVAILABLE - PICK UP VISA THE SAME DAY AFTER 3:00 P.M. (NO SAME DAY PICK-UP BEFORE 3:00 P.M.) - APPLIES TO TOURIST AND NON-IMMIGRANT B VISAS ONLY
I get a non imm o-a multi entry visa from them each year via USPS and each year it takes almost exactly two weeks from the day I mail the stuff in until my passport arrives back in my mailbox.
if you plan on arriving each October and departing each April you will need to watch the dates or you could find yourself short on one end. Doing a border run just before you leave in April will get you that extra year, provided you purchase that reentry permit. It could also affect your return date options. I take, what is for me is the easier, albeit a bit more expensive route - I get a new non imm o-a multi entry visa every year which means no worries about extensions, and no dealings with local immigration etc except for the 24 hour and 90 day reporting requirements.
after your enter before date, assuming that you left the country, as you did, and got an additional year, your non imm o-a visa is dead and done. From that point you are on an extension of stay until December 2018, assuming you purchase a reentry permit.
I do the same as you each year and I get a new non imm o-a multi entry visa via the LA Thai Consulate each time. Others will probably provide additional suggestions.