From the article you linked:
While Thailand’s Navy hit the couple with the serious charges, police colonel Nikorn Somsuk told the South China Morning Post he would have to ask the Attorney-General to proceed with the case since the outpost was technically in international waters.
“We have not met the couple yet. We have sent investigators to their home but they were not there,” he told the paper. “We don’t know what their thoughts are apart from the fact that it seems a bit extreme to want to be so isolated.”
He also hinted that the couple may not face the most serious punishment, telling the South China Morning Post “as of now, there is no evidence that their actions pose a risk to Thai sovereignty.”
Not exactly “the execution squad is kicking down the front door now” threat level.