I was driving back from Phetchaburi the other day and saw some tourist signs (blue ones) directing to a waterfall and hot springs. Since I was in the highway I couldn't catch details and soon passed, I gather I was about 50km out of BKK on route 325 or 4, I sure would like to know if anyone has seen them or been there has a name etc. I could google..

Oz

You could try google earth to find it.

Neither of these would be described as being near Bangkok, but they maybe as near as any, given that hotsprings are generally associated with mountainous areas:

1. Hin Dat Hotsprings in Kanchanaburi province - just off of the north side of Hwy. 323, about 10 km before Thongphaphum.

2. Suanpheung Hotsprings in Ratchburi province, in Ampheu Suanpheung, west of Jombung, almost to the Burmese border. (This might be the one for which you saw the directional signs.)