I was talking with my employers (they seem to be a reputable company), and while discussing work schedules and work permits I mentioned that I would need a few days off at the end of December to run to Malaysia with their employment letter to get my type B visa. They said that if I liked, I could just stay here in Bangkok and they could have an agency that is run by a former immegration official take care of everything for me.

I do basically trust them and they assured me that the stamps and visa would be legitimate, but I can't help but feel very nervous about handing my passport over to an agency and getting a possibly questionable visa. Has anybody else been offered this kind of deal?

The only 100% legal way is to do it yourself. If you go the agency route there is always the possibility of fake border stamps, fake B visa followed by detention, fines and deportation. The Thai's may well tell you mybpenrai, no probrem, everybody does it, but at the end of the day it's your head on the block.

Don't do it.

J

Have a little read through the topic on here and the sad outcomes suffered by those who used visa agents. Do it yourself, don't take the risk. You are the one in trouble not the employer if it goes wrong.