I just got back on Sept. 30 from Phnom Penh where i got my 2nd tourist visa. I have a long string of B visas (+work permits) followed by a year extension of stay for retirement. My money ran below 800,000 Baht so I got the Penang Toursit visa and then the 30 day extension. I saw the postings that Penang would not give me a second one so decided to try Phnom Penh. I asked several travel agents if they could do this for me and they all said I had to do it myself. The people hanging around outside the embassy all appeared to be motorcycle taxi and tuk tuk drivers, none put themselves forward as agents. My advice is to do it yourself. The small booth outside will give you your application and once you have it filled out they will give you a number for the waiting line, displayed on numbered signs over the windows. The lady I saw glanced through my passport and promptly gave me a number to return in the afternoon 2 days later. While I was waiting I observed the following:

One man wanted to get his passport back the next day on the grounds that he had a flight out then. When asked to produce the ticket he didn't have it so he left. Don't know if having the ticket would have worked or not. Another guy wanted a multiple entry, no way single entry visas only. He left in a huff. When I went back 2 days later they were to start giving the passports back at 3 PM but actually started at 2:45. This time there was no order to the process, just be first in line if you can. I can understand why they might want 2 days to process the passports. Just the number of international passports seemed to be about a yard wide and that didn't include the Cambodian ones which were in huge stacks!

As you are above age 50 you can likely obtain a non immigrant O visa rather than depend on tourist visas (although can not beat 'free'). That will give at least a 90 day entry and with a how of an account balance (perhaps 100k or more?) suspect some places will provide a multi entry (that might beat free).