Bangkok - off the beaten path

Siriraj Medical Museum as #2 mentioned is pretty grisly if you are into that sort of thing. It's split up into 6 different museums all nearby and all dedicated to different aspects of death and illness. Warning it's truly not for the faint hearted but defintely off the beaten path as you asked. Chao Phraya ferry to the Tha Bangkok Noi pier, walk due west then walk left into the hospital grounds and follow the signs for the Adulyadej building. Mo-Fr 9am -3pm, entry 40 baht

one more question - how about burial - any good cemeteries?
Cremation is the usual Buddhist practice, so not many cemeteries in BKK, although there are a few Christian churches in the older parts of BKK that may have a graveyard ? santa cruz church, over the river from the Pak Khlong market for example.
Although there are not many cemeteries, there are plenty of memorial shrines in the wats, not many are interesting to tourists though. But if you are out near Phra khanong, or along the sukhumvit skytrain line, then Wat Mahabut at On Nut has an interesting shrine to Mae Nak Phra Khanong, a famous Thai ghost ( http://en.wikipedia.org/wiki/Mae_Nak_Phra_Khanong ) that has been featured in many movies, ie Nang Nak. its not too far from the On Nut skytrain station, easily walkable. The Wat is on the river, and even though it is a few hundred metres from sukhumvit road it has an almost semi rural feel. .

If they want cemeteries, they can shoot out to Kanchanaburi. Thats an eye opener seeing how young some of those killed were during their internment.

What kind of morbid sicko are you?

Cemeteries are actually really interesting cultural heritage sites, as Westwood has suggested at #13. I've spent some fascinating hours in cemeteries around the world, including Kanchanaburi and Siberia (Western Australia).

Not exactly sights/off the beaten track but things to do/places to go and watch life go by:
- Lumphini park at 7am or after 5.30pm. Join in one of the tai-chi or aerobics classes or just wander round
- Get a little klong boat - I recently went from Pratunam to Ekkamai on the boat and then wandered up Ekkamai and down numerous sub-sois to Al Majis tearoom which was a very pleasant way to kill a couple of hours - all the old wooden houses over the river and wandering round the back streets of Suk makes you realise that they city is actually very residential, not just shopping malls. Tea room and gardens (Moroccan styled) is also nice, albeit pricey
- As mentioned above - the bike tours are great
- Food in the evening at Suk soi 38 (right by Thong Lor BTS)
- Healthland for a massage - various branches across Bangkok - ~400฿ for 2 hours Thai massage but in a very nice setting with properly trained masseurs - have yet to encounter a bad one. Very popular with mainly Thai clientele for good reason. No funny business - traditional massage only.
- If you're into art then there are several galleries around town - the one at Chula Uni often has interesting pieces

Whilst you can 'tick-off' many of the major sites in BK in a few days the charm of this city is that it has lots of hidden gems and sights amid the chaos - most of which you stumble upon by just walking around - e.g. Chinatown - I always see/find something new when I'm wandering round there.

War cementaries are a bit different and written in English. Thais being Buddhist tend to be cremated.

"Food in the evening at Suk soi 38 (right by Thong Lor BTS) "

i went there and the food was no different to anywhere else in Bangkok.

Muang Boran which has replicares of various temples from around Thailand gets a lot of favourable reviews. It's about 30km out of town but not too hard to get too.

A little over 24 hours lest in Bangkok and want to do a cooking lesson in town in private home - which I hear is doable. Shooting for tomorrow afternoon. Know its short notice but we've just been too danged busy to get this done - any ideas Thorn Tree helpers???

A little over 24 hours lest in Bangkok and want to do a cooking lesson in town in private home - which I hear is doable.

your best bet at that notice is to barfine some girl tonight and specify in advance that you want her to show you how to make some Thai food on the gas ring back at her shared boarding house. You can buy ingredients pretty much right round the clock. She'll agree to it if you don't shirk on the price, but she'll likely think you're a nut.

There's a cool Chinese cemetery very close to the Chong Nonsi BTS Station

In the Chareon Krung area there is the Bangkok Protestant Cemetery which is resting place of some of Thai history's more interesting Westerners like Dan Beach Bradley, William Henry Adelbert Feilding, Sir Henry Alabaster, Dr Friedrich Schaefer, M.D and Caroline Isabella Knox Leonowens - daughter-in-law of Anna Leonowens.

It's well kept but also a little spooky especially at dusk where it makes a nice quiet place for a tinny...

MikeN mentioned Wat Mahabut which is certainly worth a look in it's own right but if you go to Talaat Pra Khaong and walk to the canal you can take a long tail boat from there (past the Wat) to Sri Nakharin Road.

While there is little (nothing) to see at Sri Nakharin, the trip (about 40 mins each way) is special in it's own right as you get to see a way of life that has changed little over the years and it's easy to forget you're in a modern city. The trip is also very scenic in parts.
Getting back: when you get to Sri Nakharin just stay on the boat as usually the same boat just turns around and heads back right away. If you have to change, the pilot will tell you to get off and you cross over the bridge and get on a boat there and if you so wish you can get off at Wat Mahabut on the way back.