Visa Exemption Limit

Hi guys am looking for advice on visas for future visits,
In july and august2018 I entered Thailand twice by border on visa exemptions, and then I entered again on the 30th of december with a single entry tourist visa by air before leaving in january 2019,
I am planning on visiting again for 2 weeks in april, but I have heard there are rules on the number of times you can have visa exemption, I was wondering would the periods for the 12 month 2 land entry limit be by calendar year so january to december 2018 or is it in any 12 month period, I have the same question for the 6 month 3 air entry limit, would that be within any 6 month period or in semi annual period for example january to june and july to december.
Also can you have a combination of both entrys, so could you enter 2 times by land and 3 times by air in a 6 month period?
I would really appreciate any answers you guys might have as im a bit worried about being denied entry and im thinking of getting a tourist visa which is a bit of a hassle for me where I live, does anyone know if there if there is any limit for the number of tourist visas you can have as well?
Thank You a lot guys