Where's a good place to stay for a couple of days? Budget around 350-500 BHT, internet connection, safe, clean, spacious and within walking distance from trains in BKK city.

Presumably for that money you'll need en-suite, air-con, and UBC/Setanta.

Having satisfied my nasty side I'd suggest you log on to hostelbookers, there are a few a bit further out which might suit you.

Scroll through the recent threads in the BKK sub-forum - about a week ago there was a thread on the same topic with many good suggestions

Where's a good place to stay for a couple of days? Budget around 350-500 BHT, internet connection, safe, clean, spacious and within walking distance from trains in BKK city.

Try Asha guesthouse in the north of Bangkok near saphan Khwai Bts.

Got all you asked for plus a swimming pool

check their website ashaguesthouse.com

There's a hostel near the SE corner of Sathorn and Narathiwas that would meet your needs. Despite the word "hostel", the rooms have private bathrooms.