(the even number sois) and I want to make a U-Turn so that I will then be driving towards On-Nut on Sukhumwit Road (the odd numbered sois)...

Where is it possible to do this now?

Don't know where you are, but Soi 11, 20, 22 (traffic light) and opposite Soi 31 (traffic light) allow u-turns to the north side of Sukhumvit. Might try at Asoke (Soi 21), but don't know if police won't ticket you.

same as other , dont know where you are but one way if you are driving into town is to go to the main Asoke / Suk intersection , go left down past Sirikt Center U turn under bridge , back to the main intersection and turn right and you are then facing the correct way.

After you have done the U turn remember to keep to the right approaching the intersection or Officer Plod could spring out of his box and ping you for crossing the invisible white line which extends almost 1 kilometre, ( no one knows for sure how long this line is as no one can actually see it but Officer Plod guess about the distance out votes yours).

Sorry.

I have to go to Soi 12.... And then I will need to U-turn to go in the opposite direction (towards onNut)

Soi 12 is just opposite Robinson's.

I don't think you can do a U-turn, anywhere at all down past there.

I think you'll have to go left onto Wireless and back up Rama 4 or right at Wireless if that's possible(?) and onto New Phetchaburi.

Provided those roads are now clear and open that is.

Edit: you can get to Rama 4 by turning left just at 'Soi Zero' and going parallel to the expressway along the outside of the tobacco monoploy grounds.

I think you can turn right into Soi 11 (no U turn though), easy enough to turn around in Soi 11 or go through to Soi 3 and left at the lights.

Note, I only ever go that way after about 7pm so this may be evening only

that is what i thought. thanks, i will have to look at some maps to know where i need to navigate from soi 11.