I went to the Thai consul in Miami and told them I needed a visa for 8 months. They gave me a 6 month multiple entry visa and said this was really good for 8 months since I would get 2 more after the last entry. The visa started in the beginning of October. Last week I did a visa run to Myanmar and was given two more months but was told the visa was not good after that. The immigration guy said to come back in 2 months but I am not sure what this means. Will I be able to get 60 more days or do I need to do something else to get this extension ?

Assuming you have a tourist visa, double entry (or is it triple you have?), there is no multiple option.

You should have visited immigration before your first entry expired where you would have obtained a 30 day extension for 1900 Baht. Just before that expired you should do a border run to activate your next entry which could also be extended by 30 days. Total for a double entry visa is 6 months, a triple will net you about 9 months but only if you obtain your visa immediately before travelling as it becomes valid on issue.

What visa do you actually have? A visa issued in October will have a use by date some time in March, you must use all your entries by then, post a scan of the visa so we can see exactly what's going on.

Your visa must state the number of entries allowed so that is information we need.

It appears to have been a 3 entry visa and you have now used all three entries (you did not extend entry one or two) so you now have your 3rd 60 day entry with an option to extend that 30 days. If you want to stay longer you will require a new visa or visa exempt entry which you can obtain from another country in the area with an overnight stay or just cross border for 15 days two times or fly out and back for 30 day visa exempt entry.

Yes, it was a three entry visa. It was good until March but I have now entered the country three times. My ticket out of Phuket is May 23 and the last entry satmp is good until April 1. If I understand correctly, I can get a one month extension and then exit the country on May 1 and return with 15 more days allowed. is this right?

Yes and you can do twice if you have to.