Can I do 3 visa runs by air while in Thailand?

I came to thailand in march this year for 3 months on a single entry 60 day visa with 30 day extension....i am back in thailand from oct on the same visa with a extension to come in december until end of jan..but my flight back to England is 28th april..am i allowed to do 3 visa runs by air until then...i tried getting a 6 month visa but they needed a letter from employer..i am inbetween jobs and do not start my new job until may....so could not get the employment letter....thats why i only got the visa i got...will i have any problems..kind regards.