I've heard the Thai officials at PP in Cambodia are not so easy to deal with in this regard. I'm in northern Thailand, so the closest Thai embassy is Vientenne. I was there years ago, but am curious to know whether they're currently decent and fair about issuing or renewing Type "O" non-immigrant, multi-entry 1 year visas.

Other relatively nearby options outside Thailand include: Penang, KL, Singapore. How do they compare in this regard?

I've heard the Thai officials at PP in Cambodia are not so easy to deal with in this regard. I'm in northern Thailand, so the closest Thai embassy is Vientenne. I was there years ago, but am curious to know whether they're currently decent and fair about issuing or renewing Type "O" non-immigrant, multi-entry 1 year visas.

Other relatively nearby options outside Thailand include: Penang, KL, Singapore. How do they compare in this regard?

It has been discussed in details very recently, maybe a search will give you more details.

Multi only seem to be given by Singapore (with proof of funds) or KL

Good luck