Last update : water have occupied some districts in Bangkok city area, unfortunately including Don Mueang where the government flood center has been working at. If you want to volunteer at Don Mueang, please make sure first that you give them a call to update whether DM is accessible and flood center is maintained to be there. Below is a graphic showing the water inundation in Bangkok area taken from Bangkokpost. Click on image to see it clearly.

Source: http://www.bangkokpost.com/news/local/262704/deluge-reaches-city-north