You have to be careful in reading too much into a simple Thai sentence. Thai/Lao language has many loanwords from Sanskrit and Pali, and the word "sammuti/sammati" is one of them. It is used in non-technical contexts in everyday conversation as well, such as "Sommoot waa..." (Assuming that...). I don't think Ajahn Mun was particuarly thinking of the "Two Truths" distinction here, or that it was even an issue for him. One cannot simply back-translate a Thai sentence into its supposed Pali roots without distorting the meaning. More appropriate approach is to become familiar with how particular expressions are used in a particular Buddhist culture within their own context, and then translate them into English on the basis of that.