A friend told me that I could get a Marriage Visa easily in Malaysia, that I would only need to provide my marriage certificate and a copy of her ID card.

He told me I should ask in this forum about a bookstore that offers a Visa service to assist me. Does anyone know the name or contact info?

I've also heard that I can apply for a work permit while staying in Thailand with this Non Immigrant O Visa based on Marriage. Is that true?

A single entry can be obtained easily with copy of marriage certificate/her ID card and perhaps copy of her home register. But to obtain a multi entry non immigrant O visa valid for one year is not likely to be as easy, although it can be done. I would currently recommend KL for that rather than Penang (which I believe you are thinking about). And I would take the above documents plus short letter from wife asking for visa to be issued (helps prove relationship) and a bank account book showing you have some funds available in Thailand.

If you find work then a work permit can be issued on such a visa - but it does not provide a work permit by itself.

You can get a visa for 3 months and if you meet the requirements (a family income, that is you and/or your wife together of 40,000 a month) you can apply for an extension of stay for one year and every year after that, at the local immigration office. Do that in the last month of the period you are allowed to stay.