I managed to change at 23.60 and 23.55 at bkk on tuesday/wed.
The bank rates were terrible though! But we found a very good money changer near mbk. From the sky bridge head towards the bkk arts and cultural centre which is opposite mbk. There is a money changer at the first storey of the building beside the arts and cultural centre (you'll see a very huge advert on the side of the building).
Think it's called Siam exchange or something.
lol duno leh. she keep insisting she changed at 25.0. she just came back from thailand 2 weeks ago. she say she walk the whole golden mile complex ask all the money changer for rates then they change the best one at 25.0. will confirm again with her next week