Is there a limit of times in a year for 30 days tourist visa entering by air?

I am currently on Koh Samui on a 30 days tourist visa obtained at the airport, which will expire on 15th May.
I have to travel on 14th May out the country by plane, coming back on the 17th of May, and then on the 24th of May out again and back in on the 28th of May. Then probably would stay until 15th April which could use the 30 days tourist visa obtained at the airport plus an extension at the immigration office of koh Samui, am I correct?
Would like to ask if there is a limit of number of times in a year you can obtain30 days tourist visa comingin by plane?
Thank you in advance.