The most common methods of properly securing land are:
Having signatory authority of a domestic Thai company which owns the property (and usually the largest shareholder, but normally you will own less than 50% of the shares, normally 39% or less, see discussion below); or
Sign a 30-year (or less) lease with a domestic company or Thai individual, with an automatic option to renew for another 30 years. This is called the 2x30 ("two times 30") way.