just apply for the married visa once you get here. I was never asked for a police background check. I’ve been here for a couple decades and a police background check has never comeup. Although I’ve never been arrested, I know it’s not a requirement if you apply in country.
You’re fine. All of us old time expats are well aware that there’s a farang living here who murdered his mother in a heinous way. As if there’s any other way? It was so brutal how he did it. He served his time, got released and moved to Thailand. The Thai authorities and immigration know all about the killing and all us expats know about it too. He even bottled some guy in bar here a few years back. He still gets his visa extension approved year after year. We avoid him like the plague.