Since I live in BKK there's no reason I'd book into any hotel!
When I have had friends staying, I have always recommended the Swiss Lodge Boutique Hotel on Soi Convent across from Soi 4. It has now been rebranded as Le Siam Hotel. At about $60 per night for a week's stay or more including breakfast and internet, it is about the same as the Tarntawan. Cosy hotel with much nicer rooms although I suspect they're a good bit smaller, but very convenient for nightlife. Sorry I have no idea about joiners.