I've asked this before and never receive an adequate answer. How strict is the police background check requirement for long term visas application? Does the background check have to be completely clean or will some offense be acceptable? If so what types of issues might be acceptable or if some long period of time has elapsed, say 25 years,  is that acceptable? 

I can't speak for Thai requirements. Countries like AU and Canada to name a couple are very strict. Most offences are overlooked on police check in many countries. Thinking you will get informative replies if you detail country and offence. Most won't judge. Some will be ass####. We all make mistakes. Good luck with visa.

I assume you mean the criminal background check for a OA or a non-ox visa application.

They are not all that strict. The primary concern is imprisonment and sex offenders.

Basically it is the same as being denied entry to country as shown in the immigration act.

"6. Having been imprisoned by the judgement of the Thai Court ; or by a lawful injunction ; or by
the judgement of the Court of foreign country , except when the penalty is for petty offense or negligence
or is provided for as an exception in the Ministerial Regulations."