Can I extend my 30-day entry visa or obtain a 90-day tourist visa in Thailand after being sick?

I'm planning on going to immigration services tomorrow at Civic Center in Chain Watthana. I'm a US citizen and got a 30-day entry on my passport when entering the country. I've been sick with the flu for the past 2 weeks in my hotel and was wanting to get an extension. I'm not sure if this is a tourist visa or a 30 day Visa waiver. I was told if I go tomorrow I could either receive another 30-day extension or maybe a 90-day tourist visa. Is this information correct? I just wanted to verify before proceeding. Also I was told to be there by 8:30 a.m. is there a specific time frame for this process? I already have passport photos. Thanks.