The tenant has a contract/lease, which is legally binding on both parties, surely you are aware of that?
I would suggest that the acceptable increase would only be inline with the rate of inflation, not the mythical 10-20% more, that is if you are an ethical human
https://www.focus-economics.com/countries/thailand/news/inflation/inflation-hits-over-13-year-high-in-february#:~:text=FocusEconomics Consensus Forecast panelists see,predict average inflation of 1.3%.