How many visa exempt entry stamps can you receive in Thailand in a year?

A UK friend of mine got refused entry by flying in to Krabi Airport last year. He did not have a proper visa. He was relying on a visa excempt. Anything can happen these days!

Air is unlimited but you might attract a lot of attention of you are staying for the maximum time possible and going in and out on multiple visa exempts

2 by land, flight unlimited ...but even by air they will check on you after some excempts ... depends the officer if he believes you live and work in Thailand.

There is one rule that you can only get two Visa Exempt Entries a calendar year by land border crossings. What happend is that Immigration Officers at airports can start asking questions, like what you do in Thailand, how do you support yourself etc, when you have 6 or more Visa Exempt Entries. Then they advice you to use a Visa next time. But coming in by Air does not have a maximum of Visa Exempt Entries.