Chanote,a death and a probate question.

My wife's sister was married to a Thai man who had land near Hat Yai Airport. Both his and her names were on the chanote for the land which was owned outright. He was divorced and had 2 children and died several years ago. Probate hasn't been done on his estate which consists basically of just the land. He died intestate with no will. She now wants to sell the land what will need to be done and are his children entitled to a share of the land when sold and if so how much?

The children are grown up in their tenties and thought to be no good layabouts so can they be bought out prior to a sale?

Many thanks for any insight and feedback.