I was involved in a civil case in Bangkok 3 years ago (as the respondent), and there was no restriction placed on my passport and in fact I travelled overseas unimpeded. Obviously it would be diffient for a criminal case.
Glad I did a painless border bounce at Mae Sai / Tachileik last week, as it was reported today on the Thai Visa Advice FB group that this checkpoint (as well as Mai Sot) are now temporarily closed.