It may have changed since but about 10 years ago once an newly ordained monk received his monk papers he could get a 1 year visa and would be expected to report to immigration every 3 months to prove he was still a monk.
Before that it was much easier, but men had been ordaining to get a long visa then disrobing and continuing to use the visa, so monks who have been in Thailand longer than that probably have better conditions.
"Proper effort is not the effort to make something particular happen. It is the effort to be aware and awake each moment." - Ajahn Chah
"When we see beyond self, we no longer cling to happiness. When we stop clinging, we can begin to be happy." - Ajahn Chah
"Know and watch your heart. It’s pure but emotions come to colour it." — Ajahn Chah