yes you're on an extension, not a non-0 VISA obtained at a Thai embassy or consulate outside of Thailand. So in the case of me or the poster here it's unlimited 90-day entries over the course of the year, actually valid for 15 months if you make your last entry just before the VISA expires. I travel frequently so it's not an issue for me, and acquiring the VISA in Los Angeles costs 5,000 baht, requires only a copy of my marriage certificate, letter from my wife and bank statement showing a $700 minimum balance.
Pretty clear the poster is asking about his 1- year multiple entry non immigrant visa, not an extension, simple answer is the amount of entries is unlimited but the maximum single stay is 90 days
Just know you need to book an appointment time for notarization at the US embassy, so do that as soon as possible to ensure you can get in on time as sometimes they're fully booked!
Less than 2,000 baht, I forgot the exact amount, but something like 1,500 for the translation, filing the paperwork for you and picking it up, then a bit more for mailing it to me in Ubon Ratchathani. If you want to be sure before paying them a visit I'd just give them a call