As of about 2 and half Months ago, Jomtien Immigration was easy for the visa extension. I went on a Thursday which was exactly 1 week prior the my stamp expiring and I was there at 8.30 AM which is when the doors open. Not many there. My paperwork was all done prior, with photo and photo copies, TM30 original (although photo copy was only required.)
I was out 30 minutes later, all done and dusted and heading up to catch the songthaew back to Pattaya. FACTS: No queues, no reason to get there any earlier than 8.30 am, no waiting until next day to collect passport and visa was extended another 30 days. Easy to do yourself, cost 1900 baht.