We have a full three days in Bangkok after five weeks in Australia and NZ and would like to maximize our time in a city we will be visiting for the first (and probably only time). Can some of you experienced folks provide some information on the cost on a per-day basis of a guide for the two of us and whether the guide provides a car (if we need it). I rather not book such a service through the hotel (always more expensive, right?).

We got a private guide and car from Destination Asia. She was great. I can't recall the cost but probably dear compared to other companies as it was a huge company.

True, it's likely to be more expensive if you book through the hotel. It's also likely to be higher quality and safer. A lot of real cheap guides are available but they take you to their uncle's gem shop.

I can't recommend a specific guide as I've never used one. But I suggest paying the extra and booking through the hotel. If problems arise, they can help you resolve them. Do you know what hotel you'll be staying at?

Tour With Tong. I use her all the time, both for myself when I started coming to Bangkok, and now when friends visit. I've never heard a negative word about her services, or about the guides she employs. She is sometimes hard to contact because of her popularity and the fact that she's so selective about her guides; but stick with it. You will be well rewarded with a great and informative time. For a first-timer, try the walking/public transportation tour of Bangkok.

Obviously, the Tiger Temple tour is now not operating; and the website hasn't been updated yet. The swimming with the elephant excursion is great. Tong supports one of the elephants at the elephant rescue center. It used to be Full Moon (elephant's name), with whom I had several fun visits playing in the river, water fights, etc. Full Moon retired a few years ago; and I do not know the name of the elephant that Tong is currently supporting.

A second vote for Tong. We have used her services for 10 years. She goes to a different elephant camp now that Full Moon is retired. We were just there a few months back but I already forgot the name of the new place.
Be patient emailing her, like mentioned above, she is very popular. Someone on her team will get back with you

Staying at the Peninsula. Any idea how expensive on a daily basis a guide would be?

Depends on itinerary, transport, etc. Have a look at the often recommended "Tour with Tong" website to browse some options: http://tourwithtong.com/tourrates.htm

1000 baht = ~$30 USD

Transport, meals, admissions, etc will be additional

I have used Tong before as well, and agree with all the comments above. Very good, but be patient when contacting.

I tried Tong but they never got back to me after numerous contacts.

https://www.facebook.com/tanonrut.siripiboonruk Try BEn

I just booked with Tour With Tong. Thanks for the recomendation!

I have two tours booked with Tong as bookends to my two weeks in Thailand. The first is a full day in Bangkok with a driver, and the second is the Floating Market, Train Market, and Bridge Over the River Kwai. My question is how much to tip the guide and the driver. I've seen vastly varying suggestions.

Thai people dont make a fortune so give what you can. I did a private tour like your second day and loved it. Gave approx $30.

1000 baht

Minimum daily wage in Thailand is THB 300 (2016) so THB 1000 is very very generous. THB 500 for the guide (if guide is competent/did a great work/has met your expectations) would IMO be appropriate and 200 THB for the driver; both persons would be very happy for such tips.

I used 'Yourthaiguide' and I had a great experience. I requested a male guide who was well versed on Buddhism and could explain the political and religious symbolisms of the temples. I got an amazing guide who went to university in the US, spoke English very well, and had actually gone to high school at one of the temples. It was actually a very personal experience of him sharing his religious customs and symbols. I customized the tour to go to only the specific places I wanted to go. I had a great experience and I felt that the price was very reasonable. I chose to not have a car. We took cabs, riverboats, and walked some. It was amazing. I tipped 500Baht. I also bought his lunch. We had a great conversation at lunch. Total cost for the 7 hours was about $80. $40 in advance through PayPal and $40 (in Baht) upon completion of the day.